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Sunflower District


Wheat Disease Update

Sunflower District Stripe Rust Update (5-13-16)   Variety Responses to Stripe Rust and Fungicide Residuals

Sunflower District Wheat Update (5-6-16)   Yellow Flecks on Leaves and Purpling of Stems and Leaves

Sunflower District Wheat Update (5-5-16)   Aphids in Wheat

Sunflower District Wheat Update (5-2-16)   Overnight Lows for May 2

Stripe Rust Update (4/23/16) 

Stripe Rust Update (4/22/16) 

Stripe Rust Update (4/19/16)

Yellowing Wheat - Is It A Disease? (4/13/16)

Wheat Disease Update (4/8/16)

Wheat Disease Update (4/3/16)

Wheat Disease Update (4/1/16)

Wheat Disease Update (3/18/16)

Wheat Disease Update (3/7/16)

Wheat Disease Update (2/10/16)

Wheat Disease Update (6/19/15)

Wheat Disease Update (6/18/15)

Wheat Streak Mosaic Update (5/19/15)

Wheat Stripe Rust Update (5/15/15)

Wheat Stripe Rust Update (5/5/15)

Wheat Rust Update (5/2/15)

Wheat Rust Update (4/18/15)

Leaf Rust Update (10/29/14)

Wheat Disease Update (5/16/14)

Wheat Disease Update (5/9/14)

Wheat Disease Update (4/25/14)

Wheat Disease Update (4/10/14)

Wheat Disease Update (3/31/14)

Outlook for Wheat Rust in Kansas

Stripe Rust Update (5/11/13)

2013 Wheat Disease Update

Threat of Stripe Rust for Wheat

Viruses in Volunteer Wheat

 

Sunflower District Stripe Rust Update (5-13-16)

Variety Responses to Stripe Rust and Fungicide Residual Activity

from Jeanne Falk Jones, K-State Multi-County Agronomist

One of the things we have been talking about is how varieties respond to stripe rust.  I thought I would share some pictures with you on what you might be seeing in the field for susceptible and resistant varieties.  The stripe rust pustules on the susceptible should look quite robust, orange and these pustules you should be able to easily see or feel on the leaf.  Susceptible varieties are Brawl CL+, Byrd, Denali, LCS Wizard, TAM 111 and TAM 112.  I have attached two pictures of stripe rust on susceptible varieties – Byrd and Denali.  In some research plots on the K-State Experiment Station in Colby, stripe rust is showing up on the flag leaf in Denali that has a very thick stand.

MoreSusceptibleByrd       MoreSusceptibleDenali

Here are also some pictures of how resistant varieties are responding to stripe rust – Cedar and Grainfield.  Their rating is 3 on a scale of 1 to 9, where 1 is resistant and 9 is susceptible.  These pictures show very small orange pustules in the center of a necrotic rectangular area of the leaf.  Those pustules look pretty puny (not a technical term) and don’t seem to have the spore production of the susceptible varieties (little to no orange on my fingers when ran over the area).

MoreResistantCedar

MoreResistantGrainfield

Residual life of fungicides is continuing to be a topic of discussion.  I have attached a couple charts detailing some research from K-State.  One chart shows severity of stripe rust on the flag leaf at 30 days after application for several fungicides and the related yields.  The second is a series of charts to show the change in disease severity over time after fungicide applications.  These charts are based on leaf rust and tan spot.  However, we focus on these trials because we have multiple observations of disease within a season to help show the change in the disease severity over time. The fungicide residual life is consistent across stripe rust and other leaf diseases we have tested. FungicideResidualLife

 

WheatStripeRustStudy2013

I do have a fungicide study out on the K-State Experiment Station in Colby.  It is 16 different treatments (containing 13 different fungicides) on a thick field of Denali.  There is plenty of stripe rust to test the products ;)  Erick and I will be doing multiple evaluations on the plots to get a good look at what is going on.

 

Sunflower District Wheat Update (5-6-16)

Yellow Flecks on Leaves and Purpling of Stems and Leaves

from Jeanne Falk Jones, K-State Multi-County Agronomist

As everyone is out looking for stripe rust in their fields, we are finding other odd things!  The things I am getting the most phone calls on are yellow speckles/flecks on the leaves and purple leaves, stems and heads. 

Let’s first address the yellow flecks that are showing up on the leaves.  I have attached a picture of them.  They are very noticeable if the leaf is held up to the sun.  The specks can be a response to a couple of things - environmental stress  or stripe rust.  If they are quite small and are randomly scattered throughout the leaf surface, they are likely a response to an environmental stress.  In our case in northwest Kansas, it is likely a response to the cold temperatures last weekend. 

YellowFlecking-NoRust

If the yellow flecks are concentrated together in a rectangular or circular shape, they may be the precursor to stripe rust.  This type of shape is generally the shape of a group of stripe rust pustules.  Also, be sure to look closely for a newly emerging orange stripe rust pustule.

YellowFleckingOnWheatLeaf

I hope that doesn’t confuse anyone, I just wanted to make sure everyone understands that visible yellow flecks on the leaf does not always equal stripe rust.  Look for a grouping of them and the presence of orange stripe rust pustules.

Now let’s talk about the purpling on the wheat plants.  The purple color is also a response to stress.  I have predominately seen it on stems, but can be found on our wheat on stems, leaves and even heads.  I have attached a couple pictures of the purpling on wheat.  The purple color is because of an accumulation of sugars in that area of the plant.  Many times, this had occurred on some of the last tissue to be exposed to the elements (the last tissue to emerge from the whorl of leaves.  I began seeing it after the cold temperatures last weekend, so I believe it is a response to the cold temps.

PurpleOnWheatStems

We commonly think of purpling showing up on young corn or sorghum stems or under leaves as a response to phosphorus deficiency.  Our wheat is not showing phos deficiency this late in the season, but is responding to the cold temperatures.

Finally, if you have been looking at fields and having trouble finding stripe rust, be sure to check your variety’s resistance/susceptibility to stripe rust.  In many cases, that can help unravel the questions of why it may be easier to find in some fields and harder in others. 

 

Sunflower District Wheat Update (5-5-16)

Aphids in Wheat

from Jeanne Falk Jones, K-State Multi-County Agronomist

I have been getting questions about aphids in wheat and how to know if or when to control them. 

The aphids that are being found in wheat are predominately the bird cherry oat aphid.  These are a dark, olive green color.  The others that might be found are greenbugs.  They are a light green color with a darker bluish-green stripe down their backs.  It seems like right now we are seeing more than may than you might be expecting.  After the cold temperatures from last weekend, they are being found clustered lower in the canopy – where it is warmer.  You may be also noticing different sizes of aphids.  That is common because they give live birth, so you may find several small aphids around a single larger aphid. 

You should also be noticing lady beetles and lacewings in the field also.  That is because they are feeding on aphids.  The beneficial insects – lady beetles and lacewings – are an important and effective control of the aphids.  The aphids are like an all-you-can-eat buffet for the beneficials!  If you apply an insecticide to control the aphids, you will also control the beneficial insects.  The problem with that is the aphids can move on the wind because at certain stages of growth, they have wings.  If aphids move back into the field, before the beneficials have had the time to repopulate the field, it can create a challenging situation.

The economic threshold for bird cherry oat aphids is 20-50 or more aphids per tiller.  The lower number is for stressed wheat and the higher number is for wheat that is in good shape.  The 50/tiller is a good threshold for most of the wheat in the area because our wheat really isn’t suffering from a great deal of stress.

 

Sunflower District Wheat Update (5-2-16)

Overnight Lows for May 2

from Jeanne Falk Jones, K-State Multi-County Agronomist

Here are the air temperatures and 2” soil temperatures from May 1 to May 2.  The temperatures this morning were a bit cooler than I expected.  There are some temperatures of 28 degrees or below in Cheyenne, Sherman and Wallace Counties.  The chart shows the injurious temperatures is 28 degrees for 2 hours at the boot stage. 

AirTempsMay2

SoilTemps2May22016

Please note that the soil temperatures are taken about 5 feet above the ground, and therefore may measure colder than the air around the wheat.  The soil temperatures are still fairly warm and may help warm the air around the developing wheat head.  Although there is some wheat further along with its development, most of the wheat is not yet in the boot stage. 

It will take 10 -14 days to know the full extent (if any) of freeze damage.  Freeze damage at the boot stage can result in the following symptoms:

     - floret sterility

     - spike trapped in boot (from damage or crimping of the collar of the flag leaf)

     - damage / splitting to lower stem

     - leaf discoloration

     - odor. 

I was out this morning and afternoon looking at wheat and didn’t notice a ‘silage’ odor, leaf discoloration or any damage to the lower stems.  If you noticed any of these symptoms, please let me know. 

Here is also a picture of wheat in the boot stage and a graphic showing the different stages of development from flag leaf emergence to flowering. 

 

Sunflower District/Thomas Co/Rawlins Co Stripe Rust Update (4/23/16)

from Jeanne Falk Jones, K-State Multi-Count Agronomist

I spent quite a bit of time in the field yesterday looking for stripe rust.  I found it in trace levels in the plot in Cheyenne Co and the plot in Sherman Co.  Now when I say trace level, it means I spent probably 20 minutes looking to pull out 2 or 3 groups of pustules.  I always seem to underestimate the amount of time I spend in the field and didn’t make it to the plots in Wallace Co.  They are high on the priority list! 

When I was looking in the plots, I looked specifically at varieties rated as susceptible for the stripe rust.  Those varieties (that are popular in western Kansas) are Brawl CL+, Byrd, Denali, LCS Wizard, TAM 111 and TAM 112.  These varieties are rated as 7 or 8 on a scale of 1=Highly Resistant and 9=Highly Susceptible.  Here are some popular varieties that are rated as intermediate: KanMark – 6, Mint – 4, LCS Pistol – 5, Wolf – 4, WB 4458 – 4 and Winterhawk – 6.  Varieties that are rated as 2 or 3 are: Oakley CL – 2, Monument – 2, T-158 – 2, TAM 114 – 2, WB Cedar – 3, and Grainfield – 3. Please remember even the varieties ranked as 2 or 3 will develop stripe rust pustules, especially in years with high stripe rust pressure. 

All in all, I get lots of detailed questions about different products and the timing of applying them.  When in reality, the most important decision is the first one…Do I spray fungicide on my wheat?  Here is the list of things I use to make a fungicide decision – 10 day forecast, likelihood of high stripe rust pressure, yield potential of wheat, susceptibility of variety and stage of wheat.

     - 10 day forecast.  We are predicted to have cool temperatures and moisture – just what stripe rust loves. 

     - Likelihood of high stripe rust pressure.  If you look at the map of Kansas, we are not seeing many counties colored for stripe rust pressure.  My prediction is that will change during this next week.  Stripe rust is being found in northwestern Texas and we have had just a bit (lots) of south wind during the last two weeks.

     - Yield potential of my wheat.  I don’t like to make wheat yield predictions, so you can do that! 

     - Susceptibility of variety.  I addressed that earlier, but please remember even resistant varieties can develop stripe rust pustules.

     - Stage of wheat.  We are actually in a great stage of growth to be able to address stripe rust pressure.  We have a bit of time before flag leaves fully emerge from the whorl and stripe rust is just starting to be detected, so we have time to get a plan in place.

All in all, yield loss from stripe rust can be 50% loss with high stripe rust pressure, susceptible variety, weather conditions conducive to stripe rust development, and stripe rust moving in before or as flag leaves are emerging.  This yield loss has been seen in research at the Colby station.

Now, I know you repeated the phrase yesterday, ‘I will not spray fungicide until the flag leaf is completely emerged from the whorl’.  We discussed the fact that fungicide will not move from leaf to leaf.  I did some further investigation and the typical movement of fungicides is around ¼ to ½ inch in the leaf.  That isn’t very far.  Therefore, coverage on the flag leaf, after it has emerged, is very important.  In addition, applications of fungicides at labeled rates last around 21 days. 

Here is a list of frequently asked fungicide questions that we put together, with answers from Erick DeWolf, the K-State wheat pathologist.  I seem to seem to get lots of questions about generic vs branded products and ‘preventative’ vs ‘curative’ modes of action.  These FAQs address both of those topics. Click here for a printable version of the Frequently Asked Questions.

I have several of the K-State stripe rust publications available on the K-State Sunflower District webpage.  They include information on making the decision on fungicide treatments, varietal response to stripe rust, and efficacy of fungicides, please go to the K-State Sunflower District Wheat Disease page

Finally, if you know of someone who should be receiving email updates, please let me know and I will get them added to the list!  If you have a question about all of this (stripe rust, fungicides or anything else), please let me know!  I want folks to feel like they can make educated decisions, when deciding on treatment of stripe rust.  

Thanks everyone being part of getting the word out about stripe rust and making educated decisions on the treatment of the disease!  Remember, do not make fungicide treatments until the flag leaf has fully emerged from the whorl of the wheat plant ;)

 

State of Kansas Update (4/22/16)

from Erick DeWolf, K-State Wheat Pathologist

Reports of wheat stripe rust continued to roll in this week. The disease was already established in many parts of south central and southeast Kansas.  Stripe rust has moved to the upper in some fields within these regions now. This movement to the upper canopy is important because these leaves contribute the majority of the energy used to make grain. The other key update comes from western Kansas where the disease was reported at low levels this week. The first reports came from irrigated fields but a few dryland fields were subsequently found to have stripe rust also. 

Distribution of Stripe Rust 4-22-16

 

Sunflower District/Thomas Co/Rawlins Co Stripe Rust Report (4/22/16)

from Jeanne Falk Jones, K-State Multi-Count Agronomist

You are probably wondering what is going on with stripe rust, since we’ve had a couple days since the rain.  Well, I had hoped that we might have another week of looking for the disease, but it is now being found in trace levels in northwest Kansas. 

Now before we get into details, I want you to stop and listen closely… DO NOT spray for stripe before the flag leaf is fully out on the plant.  Wait to make a fungicide application until the flag leaf is fully out of the whorl.  This is essential for keeping the protecting yield from stripe rust with a fungicide application.  And in most fields in Sunflower District, the flag leaves are still tucked into the stem and may be a week or more before they begin emergence.

So back to the details…

I got a phone call on Tuesday afternoon about trace levels of stripe rust being found in 2 irrigated wheat fields in northeastern Thomas Co/northeastern Sheridan Co.  I thought, ‘OK, now we know active spores have been moving through the area with the wind and the irrigated wheat had more moisture to let the disease infect the leaf.’  It’s not super surprising. 

Yesterday, I got a few more pictures and phone calls to include trace levels on some other irrigated wheat fields.  Yesterday afternoon, Lucas Haag (the K-State Area Agronomist) and I went out to set up plots for a fungicide study and we found stripe rust in VERY trace levels in a field of Denali at the Experiment Station in Colby.  The wheat in this dryland field is quite thick, so the canopy was still damp from the shower that was received on Wednesday.  I then stopped at a random dryland field near Levant and found stripe rust in very low levels in the area of the field with the thickest stand.  I have also had couple reports of dryland wheat in northern Thomas Co and southern Rawlins Co with trace levels of stripe rust showing up.

So, when the new stripe rust maps come out today from K-State, Thomas County will be colored to show stripe rust has been found in trace/low levels.  I am going to spend most of the day in the field to see what else I can find in Cheyenne, Sherman and Wallace Counties.  My gut instinct is that I may be able to find stripe rust in trace levels, but we need to wait to see what I find.

What now?  The forecast looks conducive for stripe rust development.  Looking at the 10 day forecast, we are going to have cool temperature and chances for moisture.  These are the conditions that stripe rust likes.

There are a couple decisions that you will need to make over the next couple weeks.  First, are you going to spray your wheat?  If so, then when to make the decision to treat?

The decision of whether to treat or not to treat is a very important one and sometimes can be a challenging one.  The good news is that you don’t need to make it just yet because the flag leaves are not out yet!  So, we can see how the disease progresses over the next couple days.  Several factors go to into making the decision to treat – the weather forecast, the stage of wheat, the susceptibility of the variety, and the location and severity of the stripe rust. 

A general guideline that we have been using is this: if the flag leaf is out and you have a susceptible variety, the forecast is calling for cool and moist conditions and there are stripe rust pustules showing on one or two leaves below the flag leaf – make the fungicide treatment.     

Make sure to repeat after me…I will not spray fungicides for stripe rust before the flag leaf has emerged.  All fungicides have very limited ability to move around in the plant.  They have what is called limited translocation, meaning the fungicide cannot move from one leaf to another leaf on the plant.  It can move around in limited amounts within the leaf that the fungicide is applied to.  That is why it is so important to be patient and wait until the flag leaf has emerged.

I will close for now and let you know what else I am finding tonight or tomorrow.  I know you have probably heard me say, protect the flag leaf from stripe rust.  That is still very true, but don’t treat with fungicides before the flag leaf has emerged.  Otherwise, the fungicide will not get on the flag leaf to protect it. 

For additional information on making the decision on fungicide treatments, varietal response to stripe rust, and efficacy of fungicides, please go to the K-State Sunflower District Wheat Disease page.

Finally, I want to say thanks to all of you for scouting your fields and relaying what you are finding to me!  Together we have built a good network to help get field observations put together and sent out, so everyone can benefit from the information on what is being found!  Please continue to let me know what you are finding in the field.  Give me a call, snap a photo, drop me a text or send me an email…everything works!

 

Northwest KS / Sunflower District Stripe Rust Report (4/19/16)

from Jeanne Falk Jones, K-State Multi-Count Agronomist

With the moisture since last Friday, the big question is now about stripe rust in wheat.  There are increased concerns about stripe rust infections after a rain event.  To get an infection of stripe rust, there must be three things - wheat, stripe rust inoculum and moisture.  

We know we have two of the three parts of the disease triangle – wheat and moisture.  Is the stripe rust close?  Stripe rust has not been found in northwest Kansas yet this spring.  Stripe rust has been found in Colorado, north of Denver (because it overwintered in a susceptible variety) and through the central and eastern portions of Kansas.  In addition, a report from Texas on Monday indicated that northwest Texas was just starting to see stripe rust infections.  This means stripe rust is being found directly south of us – however – quite a distance south.  Therefore, this year, we are watching two fronts for stripe rust movement – the south and the west.    

We are really in the ‘wait and see’ stage to see if stripe rust makes its way to northwest Kansas.  I am in the field looking for any indication of stripe rust and having conversations with colleagues about what they are finding.  I will keep you updated on what is being found!

 

State of Kansas Stripe Rust Report (4/18/16)

from Erick DeWolf, K-State Wheat Pathologist

The recent rains across Kansas (Figure 1) will be beneficial to the wheat crop, but will also increase stripe rust activity on wheat. Stripe rust was already established at low levels in many areas of central Kansas and the recent rainfall greatly increases the risk that the disease will move the upper leaves soon (Figure 2).  This movement to the upper leaves is important because they contribute most of the energy used by the plant to make grain. The disease has already reached the upper leaves in many fields in the southeast region of the state, which received more rain in previous weeks than other regions.

Weekly Precip 4 - 12-18 - 16

Distribution of Stripe Rust 4-18-16

Where stripe rust was not yet present on wheat before the recent rains, producers have a little more time before making a decision about applying a fungicide. But it is still important to monitor for disease regularly. Fields planted to varieties susceptible to stripe rust should be scouted closely until the wheat is past the stage at which fungicides can be applied – which is flowering for most fungicides.

Where stripe rust was already present on lower leaves before the weekend of April 16-17, it may now quickly spread to the more critical upper leaves. A fungicide application now would likely be beneficial in those situations, depending on the yield potential of the crop.

In some areas of southeast and south central Kansas, stripe rust had already infected the flag leaf as of this past weekend. Where stripe rust is currently present on the flag leaves at low levels and most of the leaf’s green area is still intact, a fungicide application will still be beneficial in most cases. There is a point of diminishing return however. If the disease has already destroyed more than 25% of the upper leaves, the crop will be less likely to benefit fully from the fungicide application. In this case, the disease has already damaged a good portion of the leaf area and has likely already begun to infect much of the remaining green tissue. The remaining green tissue may still die even after the fungus has been suppressed by the fungicide.  

In short, I think we are headed for trouble with stripe rust. Growers should be checking fields and ready to spray when the weather clears. 

Wheat farmers have a lot of fungicide options to chose from although product availability may vary regionally in the state.  Most of the products are rated very good to excellent on stripe rust (Table 1).  In general, the largest reductions in disease severity and greatest increases in wheat yield or grain quality occur when fungicides are applied between full extension of the flag leaves and anthesis (when the male flower parts have just begin to emerge). Applications intended for the management of glume blotch or head scab should be made between the beginning of anthesis and 50 percent flowering. Always consult the product label for specific growth stage restrictions and preharvest intervals (PHI) before making fungicide application.

Table 1.  Efficacy of many widely marketed fungicide products against stripe rust. 

Fungicides

 

 

 

 

 

Class

Product

Active Ingredient

Rate

(fl. oz./acre)

Stripe rust rating

Preharvest Interval

Strobilurin

Approach SC

Picoxystrobin 22.5%

6.0 - 12

Excellent**

Feekes 10.5

 

Evito 480 SC

Fluoxastrobin

2.0 – 4.0

--

Feekes 10.5 and 40 days

 

Headline 2.09 EC

Pyraclostrobin 3.6%

6.0 – 9.0

Excellent**

Feekes 10.5

Triazole

Caramba 0.75 SL

Metconazole 8.6%

10.0 – 17.0

Excellent

30 days

 

Tilt 3.6 EC*

Propiconazole 41.8%

4.0

Very good

Feekes 10.5

 

Proline 480 SC

Prothioconazole 41%

5.0 – 5.7

Very good

30 days

 

Folicur 3.6 F*

Tebuconazole 38.7%

4.0

Excellent

30 days

 

Prosaro 421 SC

Prothioconazole 19%

Tebuconazole 19%

6.5 – 8.2

Excellent

30 days

Mixed modes of action

Absolute Maxx SC

Tebuconazole 22.6%

Trifloxystrobin 22.6%

5.0

Very good

35 days

 

Fortix

Fluoxastrobin 14.8%

Flutriafol 19.3%

4.0 – 6.0

Excellent

Feekes 10.5 and 40 days

 

Trivapro A EC + Trivapro B SE

Benzovindiflupyr 10.3%

Propiconazole 11.7%

Azoxystrobin 13.5%

4.0 + 10.5

Excellent

Feekes 10.5.4

 

TwinLine 1.75 EC

Metconazole 7.4%

Pyraclostrobin 12%

7.0 – 9.0

Excellent

Feekes 10.5

 

Priaxor

Fluxapyroxad 14.3%

Pyraclostrobin 28.6%

4.0 – 8.0

Excellent

Feekes 10.5

 

Quilt Xcel 2.2 SE*

Propiconazole 11.7%

Azoxystrobin 13.5%

10.5 – 14.0

Excellent

Feekes 1.05

 

Stratego YLD

Prothioconazole 10.8%

Trifloxystrobin 32.3%

4.0

Very good

Feekes 10.5 and 35 days

 

Approach Prima SC

Cyproconazole 7.17%

Picoxystrobin 17.94%

3.4 – 6.8

Excellent

45 days

* Multiple generic products containing the same active ingredients also may be labeled in some states.
** Efficacy may be significantly reduced if solo strobilurin products are applied after stripe rust infection has occurred.
Source: Foliar Fungicide Efficacy Ratings for Wheat Disease Management 2016, K-State Research and Extension publication EP-130: http://www.bookstore.ksre.ksu.edu/pubs/EP130.pdf

 

 

Yellowing Wheat - Is It A Disease? (4/13/16)

I have also been getting questions about the yellowish cast that is being seen in many throughout the area. If you look closely, the lower leaves are the ones with the most yellowing – from light yellow to gold colored - showing up. Those leaves are also senescing or turning brown. The tips of the leaves, located just above the yellowing leaves, may also be showing tip dieback. However, all of the new growth is looking green and healthy.

I thought many of the symptoms didn't look quite like a disease (fungal, virus or bacterial), so I sent in several samples to the K-State Plant Pathology Diagnostic Lab. The results came back negative for all viruses (Wheat Streak Mosaic, High Plains Mosaic, Triticum Mosaic, Barley Yellow Dwarf and Soilborne Mosaic). They were also negative for fungal disease (all rusts, tan spot, septoria and root/crown rots). Finally, no bacterial diseases were found.

The results came back as environmental stress. Environmental stress can be related to many things, but I think it our wheat has actually been through quite a bit in the last month. The temperature swings have been below freezing to upper 70s. The wheat has also been exposed to blizzard conditions in the northwest corner of the state on March 23-24. In addition, we are continuing to see drought stress showing up on the edges of field or in compacted areas. Finally, nitrogen that was applied as a topdress application has likely not yet been moved into the root zone because of lack of rainfall. Nitrogen stress also shows up as yellowing and death of the lower leaves.

I also wondered if the yellowing was related to one variety or varieties with similar parentage. However, I have found or received samples from a wide array of varieties – SY Wolf, T-158, TAM 112, Denali, Winterhawk, Grainfield, Byrd and Brawl Cl+. That is quite a wide variety of parent lines as well.

In addition, it is not confined to one or two counties. I have looked at or received samples from Cheyenne, Sherman, Wallace, Logan, Thomas, Rawlins, Decatur and Sheridan Counties.

All in all, when I sent the samples into Manhattan, the plant pathologist called to say that I have been sending her some of the best looking wheat that she has seen in the lab. She thought a good drink of water would do our wheat a lot of good!

yellow wheat pic 1

yellow wheat pic 2

yellow wheat pic 3

 

 

Wheat Disease Update (4/8/16)

Jeanne's Report

Here is your stripe rust update. The map from April 8 is still showing the corridor of stripe rust infections in Central Kansas. There have been a few more counties added to the map from last week, but they are mostly filling in counties in south central and north central Kansas.

In addition, in the report that I received from Colorado this morning says that the reports of stripe rust in the Prospect Valley, around Keenesburg, seems to be staying localized and not moving very much. That is good news for us! The more concerning news from Colorado is that a trace amount of stripe rust has been found at Stratton. We are going to keep an eye that way to see if the trace levels start to increase or move.

So, what does that mean for us? Right now, we are still in the hurry up and wait phase to see if stripe rust starts to show up-which is a phase that I am very happy to be in! The moisture in the forecast is going to be great for the wheat. However, moist conditions are also good for stripe rust. We are going to continue to listen to the south (and now west) for new reports.

If-and it's a big "if"- stripe rust starts getting closer, it is important to remember the most important part is to protect the flag leaf. We are still quite a ways from flag leaf emergence. In nearly all wheat fields in the Sunflower District, the growing point has moved above the soil surface and many have placed the first joint above the soil surface. This is still many days from a flag leaf showing. Generally, we (K-State) does not recommend fungicide treatments for rust diseases until the flag leaf has emerged. A majority of the energy and nutrients to fill the head comes from the flag leaf, so that is why it needs to be protected.

 

K-State Whole State Report

The wheat crop in Kansas is now at the flag leaf emergence stage of growth in much of southern and central Kansas. The crop is at mid- to late-jointing in the west central and northwest regions of the state. Stripe rust continues to be our primary focus this week with new reports from additional counties and further disease development in central Kansas. The disease is still limited to the lower leaves for the most part with occasional mid canopy leaves with trace levels. The incidence of stripe rust on the lower leaves of susceptible varieties ranges from 1-30%.

stripe rust map 4-8-16

Leaf rust was observed at multiple locations in central Kansas this week also. As with stripe rust, leaf rust is also on the lower leaves. Only trace levels have been found so far in most plots. We did observe a few fields and plots in Reno and McPherson counties with incidence of leaf rust approaching 90% on the lower leaves. The severity of the infection was still low (<10%) in most cases.

 leaf rust distribution map 4-8-16

The dry conditions may be slowing the spread of leaf diseases temporarily, but the growers should be watching the situation carefully. Be prepared to apply fungicide if disease continues to progress.

 

Erick De Wolf, K-State Extension Plan Pathology

Romulo Lollato, K-State Wheat and Forages Specialist

 

 

 

Wheat Disease Update (4/3/16)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I have not found any signs of stripe rust here in northwest Kansas. However, it is important to keep checking fields for any disease.

Stripe rust is showing up through a central corridor of the state, reaching from Oklahoma to Nebraska. In addition, southeast Kansas has reports of infection levels on the upper leaves of the disease. In some cases, it is showing up one or two leaves below the flag leaf. They will soon begin making decisions on fungicide treatments.

There is still a report of stripe rust coming from northeast of Denver. Their update said that the symptoms have spread a bit, but not a great deal. Windy conditions may have moved the spores, but there has not been a great deal of moisture in the area to allow the spores to infect the leaves.

 

 

Wheat Disease Update (4/1/16)

from Erick De Wolf, K-State Extension Plant Pathology and Romulo Lollato, K-State Wheat and Forages Specialist


The Kansas wheat crop is progressing rapidly through the jointing stages of development in much of the state. Wheat in the southeast portion of the state is at or fast approaching flag leaf emergence. The crop is generally considered to be two or three weeks ahead of schedule.
 
Scouting reports indicate that stripe rust has become established in the 2016 wheat crop. This past week, stripe rust was reported in many counties in central and eastern Kansas (Figure 1).

dist map of stripe rust 4-1-16

The disease is still at low levels in most fields with a few exceptions in southeast Kansas. This early establishment of stripe rust increases the risk of severe yield loss and growers should continue to monitor the situation carefully. If weather conditions become favorable, the disease could spread rapidly from the lower leaves, where it is now established, to the upper leaves critical for grain development.


Growers should check their fields for stripe rust as the crop approaches flag leaf emergence and heading. Fields with stripe rust still in the lower canopy at heading are at a moderate risk for severe yield loss. This means that fungicide applications are likely to result in a profitable yield response (>4 bu/acre) 50-60% of the time. A field is at high risk for severe yield loss if the disease is established on the upper leaves prior to heading. Fungicide applications are likely to result in a profitable yield response 60-90% of the time under these conditions. Variability in fungicide response can primarily be attributed to differences in local weather conditions and susceptibility of the wheat variety.

Growers in most areas of the state have some time to gather more information about the status of disease and costs of fungicide application before making the decision to spray. Fields with good yield potential may benefit from a fungicide application if the disease continues to spread.

More information about making fungicide decisions in wheat can be found in the K-State Research and Extension publication, Evaluating the Need for Fungicide Applications in Wheat, at http://www.bookstore.ksre.ksu.edu/pubs/MF3057.pdf.


Erick De Wolf, Extension Plant Pathology

Romulo Lollato, Wheat and Forages Specialist

 

 

 

Wheat Disease Update (3/18/16)

The wheat crop is growing rapidly throughout Kansas. The crop in the more advanced fields are approaching jointing in the northwest and are about a week away from flag leaf emergence in the south central and southeast portions of the state. The crop is generally considered to be about 3 weeks ahead of schedule with respect to normal growth and development. There are multiple reports of leaf rust and stripe rust in Texas, Oklahoma, and other surrounding areas. 


Disease presence and implications for growers
The Crops Extension team has been busy scouting for disease in recent weeks. We are finding active leaf rust  and stripe rust in the state (Figures 1 and 2). Leaf rust was reported in west central and northwest Kansas, with most activity in counties bordering Colorado. Low levels of leaf rust were also observed in research plots in Riley county, which is located in northeast Kansas. The winter has been very mild in Kansas and it is very likely that the leaf rust has overwintered in the state. Stripe rust was reported in multiple counties this past week. Stripe rust is generally at very low levels with most activity reported in the southeast portion of the state (Figure 2).


Tan spot and powdery mildew have also been reported in some areas of the state.

distribution of wheat leaf rust 031816

Figure 1. Risk of leaf rust in Kansas-March 18, 2016

 

Distribution of wheat stripe rust 031816 

Figure 2. Risk of Stripe Rust in Kansas-March 18, 2016

What does this mean for wheat growers in Kansas?
The early reports of leaf rust and stripe rust are cause for concern. The risk of disease outbreaks and disease-related yield loss increases dramatically when the rust becomes established in the state prior to heading. Reports of increasing disease in Oklahoma and Texas suggest that, if weather conditions are right, more disease may move into the state soon.
 
What might growers consider doing to prepare for possible disease problems?
The most important thing growers can do at this stage is check their fields for disease. Scouting can help inform critical decisions about fungicides that will need to be made soon. Checking wheat varieties reaction to rust can help growers set priorities for scouting. Everest, Armour, TAM 112, and TAM 111 are widely planted in state. All of these varieties are susceptible to stripe rust and should be monitored carefully for symptoms of stripe rust. In western Kansas, where leaf rust has been more active, TAM 111 and TAM 112 are a top priority for scouting for disease because these varieties are susceptible to both rust diseases.
 
Fungicide options and considerations
Growers may also begin to gather information about fungicides options. Growers have access to many excellent product options. However, the price of these products and applications will be particularly important this year because the value of wheat grain is lower relative to some recent years.
 
The timing of these applications is also very important. Research has demonstrated that a single fungicide application applied between boot and flowering stages of development results in maximum yield benefit.
 
Fungicide applications made prior to jointing, followed by second application may also be an option. In K-State tests, these two application programs rarely result in much additional yield. It is the second application, between boot and flowering, that does the heavy lifting in terms of yield response. Also, keep in mind that label restrictions often specify the total amount of active ingredient that can be applied to a crop. Using a low-cost option early could limit the product options later in the season when a second application is needed to protect the upper leaves.
 
One final note of caution. Keep an eye on the forecast. It may be unwise to apply a fungicide when there is a significant risk of a freeze event or other hazard on the horizon that can limit the crop's yield potential. It is a good idea to be checking for disease and making other preparations for a potential fungicide application if conditions are right. It will be important to gather information and make a good decision in what looks like a challenging wheat production year.

 

Erick De Wolf, Extension Plant Pathology

Romulo Lollato, Wheat and Forages Specialist

 

 

Wheat Disease Update (3/7/16)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I received some reports of leaf rust to the south of us (Greeley Co) last Friday, showing up in the greening up wheat. It is showing up in the biggest and "rankest" wheat, that had plenty of growth last fall. It is not showing up in the smaller wheat.

Many times, I see leaf rust on wheat in the fall. The "freeze and thaw" cycles and dehydration are enough to kill off the fungal disease because of tip dieback of the older leaf tissues during the winter. Leaf rust must have live and viable tissue to continue to reproduce.

I was out looking at wheat a great deal of the weekend in Sherman and Cheyenne counties. I didn't find any leaf rust. In two cases, I went to fields that I found leaf rust last fall, but am not finding it now. I plan to look at wheat in Wallace county early this week and will let you know what I find.

While there is concern to already see leaf rust, it should be noted to continue to increase, it has to keep up with the wheat growth. It first has to move off the older growth to the newly emerging leaf growth. Then we need to have the right conditions for it to continue to produce viable spores for new infections. It needs moisture on the leaf surface for infections. It may be more concerning if it moves onto the newly emerging wheat and there are no more temperatures projected to be below freezing.

I was questioning the viability of the spores that are currently being produced. I spoke to Erick De Wolf, the K-State wheat pathologist. He said that the spores being produced are likely viable, but not all of them will cause a full-blown pustule. The spores themselves are subject to dehydration and cold temperatures. He also noted that the release of spores is a continual cycle (meaning that they are not all released in a very short window, but are released over a period of a couple days). This may allow more leaf rust spores to find suitable conditions for survival. One of the best things for suppressing this disease is overnight temperatures below freezing.

All in all, I don't think applying a fungicide for leaf rust before jointing is a good use of your money. Leaf rust infections before jointing have very little (if any) impact on yield. I know budgets are tight this year. I am also concerned that this year may be setting up to be a stripe rust year. Because of that, save your "fungicide line" in your budget for when we can make a difference in yield...at flag leaf.

If you are going out to look at your wheat for the leaf rust, I would pick the earliest planted wheat that you have because it generally has the largest plants. Look at the bottom leaves of the plant for raised pustules that will appear randomly scattered on the leaf surface. They will be orange if they are releasing spores. I have attached a picture that was sent to me from a field in Greeley county.

Early Spring Leaf Rust

Finally, if you are out and about in your wheat field and find something interesting, please let me know! I really appreciate your reports. It can really help getting in front of diseases and insects, instead of playing catch up.

P.S. There are other diseases that early fungicide applications can provide important levels of control. One such disease is tan spot and it is generally found in continuous wheat fields.

 

Wheat Disease Update (2/10/16)

from Jeanne Falk Jones, K-State Multi-County Agronomist

How soon will we know if stripe rust will be affecting wheat this spring? Actually, the end of February and the month of March can be telling months, when looking at predictive models for the disease.

This is because we are looking to see how stripe rust is progressing in Texas and into the southern portions of Oklahoma. If they have moist growing conditions, then the outlook for stripe rust increases for our area. If conditions are dry, there can be leaf tip dieback on the wheat. This usually happens on the infected tissue and can decrease the likelihood of stripe rust making it to northwest Kansas.

There has been a great deal of work at K-State in developing prediction models for leaf and stripe rust. K-State Extension wheat pathologist, Erick DeWolf is heading up those efforts. His graduate student has been validating the models over the last couple of years. Consequently, these models are becoming more refined and better at predicting outbreaks of the diseases.

Currently, (in mid February) there are trace levels of stripe rust found in very southern Oklahoma and Texas. In many cases, these trace levels were also present last fall. The presence of the stripe rust right now should not be concerning because this is not uncommon.

All in all, we should not be concerned about a stripe rust outbreak at this time because it is just too early to tell. Stay tuned for updates about wheat diseases throughout the growing season!

 

Wheat Disease Update (6/19/15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I realized that there were points that I left out on Fusarium Head Scab. One key characteristic to identifying head scab is the white heads or portions of the head being white, with orangish – pink colored fungal growth on the outside of the glume. I have attached a picture of a head that I took out of dryland Winterhawk today. It has the orange fungal growth on the glume and where the mesh hooks onto the rachis (stem).

The seeds inside these infected mesh are many times shriveled and can be covered with additional fungal growth. I attached a picture of a kernel that was out of the head in the previous picture. It looks a bit furry. As they mature, they begin to have a chalkish white appearance. These kernels are also lighter and can be blown out the back of the combine at harvest.

 head scab on kernel

There are questions about saving seed from wheat infected with head scab. The wheat can be saved, but should be definitely be cleaned. In addition, it should be treated with a fungicide seed treatment. The seed treatment is a recommended practice because the head scab actually affects wheat at two stages of growth. One is at flowering, which is what we are dealing with now. The other is in the fall at seedling emergence. Seedlings that become infected are more susceptible to seedling blight. However, seed treatments will only protect in the fall and not protect against infection at the flowering stage.

Finally, there are also concerns about the quality of the grain. Wheat infected with head scab may contain mycotoxins DON (vomitoxin) and zearalenone (an estorogen analog). Neither of these are highly toxic, but can reduce performance when fed to livestock. Incidentally, some grain elevators test for wheat infected with head scab.

 

Wheat Disease Update (6/18/15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I bet you thought you were done hearing from me on happenings in wheat, but not quite yet! We have a few things still showing up in wheat, even as we are getting closer to harvest. These are being found in the head...head scab and black chaff. Both of these diseases are generally found in irrigated, but I am finding them in dryland this year.

Head scab is a fungal disease that is generally found in irrigated wheat drilled into corn stalks. This is because the disease that causes fusarium stalk rot (turns the inside of the stalks pink with rot) also causes fusarium head scab. Head scab is characterized by part (or in some cases most) of the head being white. The kernels inside the white part of the head are likely beginning to shrivel or have fungus growing on them. You may also notice an faint orangish-pink color on the outside of where the kernel is being formed (glume).

The infection of this disease happens at flowering. Basically spores are floating around in the air and need moisture to infect the pollinating flowers. We had the moisture this year and apparently an abundance of head scab spores. I did not anticipate this disease showing up in places other than wheat following corn, but this year it seems to be. Yesterday, I looked at irrigated wheat following soybeans and dryland wheat in a 3 year wheat-corn-fallow rotation that both had head scab. There were corn stalks very close or adjacent to the fields that may have served as the source of the head scab inoculum.

I have attached a picture of what I found yesterday. Here is a link to an eUpdate article that discusses this disease a bit more: http://ksu.ag/1d69ZP0

 head scab

This disease is generally controlled by fungicide application. Now, you may be thinking that you sprayed fungicide for stripe rust. Many of the same fungicides that control stripe rust also work on head scab. The fungicide application needed to be applied after head emergence and prior to flowering. The fungicide only protects the parts of the plant that it is applied to because it has limited translocation (same as why we recommend treating for stripe rust after the flag leaf has emerged to protect the flag leaf).

The second disease that I am getting questions on is black chaff. This is a bacterial disease that causes the glumes around the kernels to turn a dark purplish-black color. There are also purplish-black lesions on the stem and dark colored bands/striping on the awns of the infected head. In many cases, you can also see brownish-colored streaks on the leaves...although this is difficult to see this year because of everything that has attacked the flag leaf. I have pictures of all of these symptoms attached to this email. The purpling on the heads is generally what is first noticed.

 black chaff and kernel under microscope

Since this is a bacterial disease, fungicides do not control it. In fact there is nothing that can be done with this disease. It is also a disease that likes wet environments. I have found it on both in dryland and irrigated fields. The bacteria enters the plant through openings (through wounds on the plant or even through the stomata – where gas exchange happens).

 black chaff head and stem

 

Here is a link to more in depth information from University of Nebraska on black chaff: http://www.ianrpubs.unl.edu/epublic/live/g1672/build/g1672.pdf

There are other things that can cause white or off colored heads. Freeze can cause white heads. If the heads are affected by freeze, there will be no kernels in the head. This is because freeze affects the pollination – an no pollination means no kernels. I think we may also still be seeing effects of the winter injury from the cold November temperature drop. I think this because I am finding tillers of plants that have put on heads and in some cases the heads are partially filled – but the tillers have now died. They also easily detach from the plant at the soil surface. That makes me think they were injured from the cold temperatures and rot set in (with the moisture) to finish off the tiller.

All in all, we have some really nice wheat across the area. Lately while looking at wheat, I've realized that it wasn't that long ago I was planning for an early harvest because of dry conditions. What a difference a bit of time (and rain) makes!

 

Wheat Streak Mosaic Update (May 19, 2015)

from Jeanne Falk Jones, K-State Multi-County Agronomist

As everyone is out looking for stripe rust in their fields, wheat streak mosaic is also being found.  The wheat streak mosaic is characterized by yellowing plants, with leaves that have a mottled yellow and green appearance.  In many cases, the virus showing up in patterns that we are most accustomed to.  These include increased severity on one side of the field, where it seems all plants are infected.  The severity of the symptoms generally decrease as you move across the field, away from the source. 

The source is generally thought of as volunteer wheat because it harbors the wheat curl mite.  The wheat curl mite is a tiny insect that moves the wheat streak mosaic virus.  As it feeds on new wheat material, it transfers the virus to the plant.  There are other plants on which the wheat curl mite can live.  These include corn and several grasses found in the road ditches – including foxtails and sandbur.  These tiny mites need green material to live on and die after just a few days if they do not have the green tissue.  There was also no shortage of volunteer wheat last summer, likely because of the hail events in June and very early July.  The mites also rely on wind to move them to their next food source. 

The thing that is challenging this year is the fact that the patterns in the field do not match up with what we typically think of as wheat streak mosaic patterns.  It seems the most common pattern in the field is really no pattern at all, but randomly scattered groups of plants with the mottled green and yellow symptoms on the leaves.  These plants are also fairly easy to see because the yellowed plants stand out against the other green, healthy plants. 

Upon visiting with both an entomologist and plant pathologist, it seems the cause of the scattered plants is likely related to a heavily infested, but distant source of the wheat curl mites.  The wheat curl mite population diffused as it moved further from the main source.  With the long, warm fall the wheat curl mites would have had ample time to move around and infect wheat plants.  In addition, there is likely something that may have prevented the population from getting well established in the wheat.  It is possible that the cold snap in November may have helped suppress the mite population or prevent it from getting established in a field. 

In addition, there is a lag period between the infection of the wheat streak mosaic and the expression of the symptoms of the virus.  The virus must reach a certain level within the cell before the symptoms will show on the leaves.  The virus also replicates at different rates, based on the growth stage of the wheat plant and the temperature.  The rate of virus replication increases with increasing temperatures.  That is why it seems that the symptoms started showing up after some rain (wheat started growing) and warmer temperatures (virus increased in rate of replication).

Finally, there is nothing that can be done to treat the wheat streak mosaic virus.  Once it is in the cells of the plant, there is nothing that can be done to control the virus.  Minimizing stress on the plant is the best medicine to minimize the effects of the disease. 

 

Wheat Stripe Rust Update (5-15-15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

You haven’t heard from me for a few days and there are a couple things that I need to bring you up to date on.  Stripe rust is still being found in nearly every field.  In many cases it is progressing up through the canopy.  It is beginning to be found on the flag leaf in some fields.  As I looked at wheat today, some of the pustules erupting on the flag leaf are at the blister stage (although others were a bit further along and releasing spores).  This ‘blister’ stage is just before it breaks through the cuticle of the leaf.  The pustules will be slightly raised and will be shiny.  Also, if you run your finger across them, it will not turn orange because the spores are not yet being released. 

 

The stage of these pustules correspond to the foggy rainy day last Tuesday.  This is because the time from the spore infecting the leaf to the pustule releasing spores can range from 7 to 14 days.  In addition, the 10 day forecast looks fairly conducive to the stripe rust with rain chances and fairly cool temperatures.  The stripe rust will continue to be active because we do not have warm enough temperatures in the forecast.  We need overnight lows above 60 to shut down the stripe rust.

 

So how do you make the decision to spray or not to spray fungicides?  Look at the yield potential of the field and the cost of spraying.  From some information that I received from Eric DeWolf (K-State Wheat Pathologist), if the stripe rust is in the upper canopy before/at flowering, spraying will most likely result in a 10% yield response or greater.  For 30 bushel wheat, that would likely be a response of 3 bushel or more.  If it is in the lower canopy, spraying with a fungicide will only result in the desired yield response 50-60% of the time. 

 

I am getting the question of: If it’s on the flag leaf, is it too late to spray for stripe rust?  Not necessarily.  If nearly every flag leaf is severely infected, then it may be too late.  In most of the fields that I have been in over the last 2 days, that is not the scenario that I am seeing.  It is getting much easier to find, but is not being found on every flag leaf. 

 

By spraying a fungicide, it will not green back up the area infected with stripe rust.  Also, in my mind, I want the fungicide to work like paraquat on weeds.  Whatever it touches, I want it to control it IMMEDIATELY.  That is not necessarily the case with fungicide.  The stripe rust may continue to progress a bit after the fungicide is sprayed, however it will be suppressed.  From how I understand how a fungicide works, some of the rust pustules will be too fully developed for the fungicide to prevent it from erupting from the leaf surface.  However, it will slow it down and suppress the population.  Also, some fungicides will prevent the spores from getting into the leaf and others control the spores after they infect the leaf…this is a difference of likely less than 24 hours.  We often hear of ‘preventative’ and ‘curative’ fungicides like they are mutually exclusive modes of action, when in reality the preventatives have curative properties and visa versa.     

 

When making the decision to treat, be mindful of the preharvest intervals.  For some products, it is wheat growth stage Feekes 10.5 (beginning flowering) and for others is it 30 to 40 days prior to harvest.  In addition, I feel very comfortable with generic fungicide products.  From everything that I have seen, there seems to be no difference in the efficacy of the products or in the residual (in general 14-21 days of residual).  In addition, the generics are easier to ‘pencil out’ because of the lower prices.

 

I have attached the K-State Foliar Fungicide Efficacy Ratings publication.  This outlines the different fungicide products, their efficacy on stripe rust and the pre-harvest intervals.  I also have pictures of the progression of stripe rust on my K-State Sunflower District Agronomy page at: http://www.sunflower.k-state.edu/agronomy/wheat/stiperust.html

 

Wheat Stripe Rust Update (5-5-15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

There are lots of questions surrounding stripe rust.  Is it here? How bad is it? Will it progress? Is my variety susceptible?  Do I need to spray a fungicide? So let’s try to address those questions. 

‘Is it here?’  Yes, I am finding stripe rust in basically every field that I check.  To know if you have stripe rust, look for raised orange pustules on the leaf surface.  You can run your fingers over the area to feel the slight raises on the leaf surface and your fingers will be orange from the rust spores rubbing off the surface.  Many times the stripe rust will occur in a longitudinal ‘striped’ appearance following the veins on the leaf.  However, the stripe rust can be found clear across the leaf surface.  There are pictures for helping identifying it here: http://bit.ly/1JoKJOv

‘How bad is it?’ And ‘Will it progress’ are questions that go hand in hand.  Right now the stripe rust is being found on one to three leaves below the flag leaf.  This is important because it is not yet being found on the flag leaf.  The flag leaf is important to protect because between 60 and 80% of the nutrients that go into the head, come from the flag leaf.   About a week ago, it was being found in trace levels, meaning that I had to look for quite a while to find a group of stripe rust pustules.  Now, it is getting easier to find. 

The next question is what is the future of this disease – will it get more severe?  That is really the million dollar question.  As I am writing this article it is Tuesday afternoon.  It was very foggy this morning and is now misting/raining and cool outside.  These are the conditions that stripe rust loves.  It really likes cool temperatures – with overnight lows from 40 to 60 degrees – and it takes moisture for the rust spore to infect the leaf.  The forecast is for these type of symptoms to be around for the rest of the week. 

Now, ‘Is my variety susceptible?’  It appears that the race of stripe rust is different than the last couple years.  Stripe and leaf rust are notorious for shifting the race of the disease to overcome the resistance in popular varieties.  As of now, we know Everest, Armour, TAM 111, and TAM 112 are susceptible.  However, stripe rust is also being reported on varieties with intermediate or moderately resistant reactions to the disease, including WB4458, WB-Cedar, and 1863.

How do you make a decision on treating with a fungicide?  This is really a tough question with the wide variety of potential wheat yields across the area.  Depending on the cost of fungicide and application, in some cases, it will take 2 ½ to 3 bushels of wheat to pay for the fungicide application.  In other more costly applications, it will take around 5 bushel per acre. 

Research done at K-State suggests that the yield response for stripe rust can be more than 20% when conditions favor disease development on susceptible varieties.  Fungicides applications are most likely to result in a 10% yield response or greater if stripe rust or other diseases are established on the upper leaves prior to flowering. If the disease is only present in the low to mid-canopy at these growth stages, a fungicide application will only result in the desired yield response about 50-60% of the time.  This is very dependent on the weather forecast for the next 10-14 days.

If you are planning to spray a fungicide, make sure the flag leaf has emerged.  Fungicides will move around within a leaf, but will not move from leaf to leaf.  So, to ensure the flag leaf is protected, make sure the flag leaf is exposed to the fungicide application.  In addition, there are lots of products that are available to farmers that have very good to excellent efficacy ratings.  There are some important differences in cost to consider. The cost of a fungicide treatment (product + application costs) generally ranges between $10-$25 per acre. Products containing the active ingredient tebuconazole, or propiconazole are often the least-cost options and have high efficacy ratings. 

 

Wheat Rust Update (5-2-15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I have been checking fields all of this last week and have been getting reports in from others checking fields.  So, the short answer is that stripe rust is being found throughout the area – HOWEVER – in trace levels.  I have found it in Thomas, Rawlins, Cheyenne, Sherman and Wallace Counties.  In many fields, it is not easy to find.  For example, I spent over 30 minutes in a circle of irrigated wheat to find only three clusters of stripe rust pustules.    

 

In addition, the rust is being found in the lower part of the leaf canopy.  It is on 2 to 4 leaves below the flag leaf.  This is important because the flag leaf (or even one below the flag leaf) has not been affected.  In some cases, the rust pustules look like they are just under the surface of the leaf (shiny appearance) and have not yet erupted.  In other cases, the pustules are further through their development and have released the spores (more fuzzy appearance).

 

The conditions that are conducive to the development of stripe rust include moist conditions and temperatures between 50 and 60 degrees.  The recent rainfall events and moist, foggy days have favored rust development.  In addition, it seems that thick irrigated wheat would have the best situation for the development of stripe rust because in many cases the canopy is very slow to dry out after being watered or a rain shower.  The irrigated wheat is the wheat that I have been checking the most…mostly because I think that is where I will find the stripe rust first.

 

If we get to a place to start treating rust (which at this point is a big IF), it is very important to wait until the flag leaf has fully emerged.  The reason for this is because the fungicide will move around in the leaf that it is applied to, but will not move from one leaf to another leaf.  It is important to protect the flag leaf.

 

All in all, I think we will be able to draw more conclusions as we move into next week.  In all reality, if stripe rust was moved north with the storm system two weeks ago, we would just now be starting to see the symptoms because it can take up to 2 weeks for the pustules to show up after the spores have infected a cell.  In addition, we still have time to make any decisions about treatment, IF we arrive at the treatment threshold.  Many fungicides must be applied just prior to flowering. 

Also, there is a K-State Agronomy eUpdate from Erick DeWolf, wheat pathologist, that was released on Friday, May 1: http://ksu.ag/1EC5WmN

 

Wheat Rust Update (4/18/15)

from Jeanne Falk Jones, K-State Multi-County Agronomist

I have been getting a few questions about leaf and stripe rust and the likelihood that we will find it in northwest Kansas.  Follow the links for maps for stripe ( http://www.arcgis.com/home/webmap/viewer.html?webmap=aa8bcfd29fe94fd1ad397992ae76c3a1&extent=-130.5965,13.5965,-75.8407,54.784 ) and leaf ( http://www.arcgis.com/home/webmap/viewer.html?webmap=2c390053d2ca4cb3a2f333091bcdf671&extent=-125.2482,13.2906,-70.4924,54.6022 ) rust observations and a report from yesterday from the USDA ( http://www.ars.usda.gov/SP2UserFiles/ad_hoc/36400500Cerealrustbulletins/15CRB2.pdf ) . 

Up to this point, stripe rust has only been found in some nursery plots in the Manhattan area in Kansas.  Leaf rust has been observed in northeast and south central Kansas.  In addition, for Oklahoma and Texas, the observations nearly all are in central or the eastern parts of the state. 

Since earlier this spring, the predictions have taken the tracks for both stripe and leaf rust to the east of northwest Kansas.  And so far, that seems to be the case.  However, there is concern with this last weather system that is moving though the area.  The way it has set and spun makes me wonder if rust spores will be moved north with the southerly winds.  This would likely take the rust into south central or southeastern Kansas (not northwest Kansas)  However, we will not know for at least two weeks if that was the case.    

Additionally, here is the link to the report for the state of Kansas from Erick DeWolf in K-State Agronomy’s eUpdate newsletter: https://webapp.agron.ksu.edu/agr_social/eu_article.throck?article_id=530

 

Leaf Rust Update (10/29/14)

I have been finding a small amount of leaf rust in wheat fields in the last couple weeks. I have attached a picture of what I am finding. You will notice that it is showing up on the older leaves of the plants. It is not uncommon to find leaf rust in the fall and this fall has been especially conducive to the development of the disease. Leaf rust loves the weather that we have been having...with dew and fog in the mornings and highs between 65 – 80 degrees.

Nearly 60% of the time in Kansas, leaf rust does not survive the winter because of the cold temperatures and leaf dessication. Generally, leaf rust does not survive the winter in northwest Kansas.

Also, fungicide treatments are not recommended in the fall. Fall infections are generally light infections and do not cause yield losses.

Wheat Rust

-Jeanne Falk Jones, K-State Multi-County Agronomist

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Wheat Disease Update (May 16, 2014)

There has been no stripe, leaf or stem rust reported in Kansas or in the panhandle of Oklahoma. In far northwest Kansas, the wheat's stage of growth ranges from the flag leaf nearly fully emerged to beginning heading. This is the typical time of fungicide applications. However, with no disease pressure, not applying fungicides this year is a sound business decision with less than 3% chance of a yield increase.

-Jeanne Falk Jones, K-State Multi-County Agronomist

 

Wheat Disease Update (May 9, 2014)

A note from Jeanne: there has been no rust found in Cheyenne, Sherman, Wallace, Rawlins or Thomas Counties, as of May 9.

The wheat crop has raced ahead in growth stages this past week. The growth stage now ranges from flag leaf emergence in the north to early stages of kernel development in the south.. The hot, dry weather continues to be the major issue in the state although spotty rains have brought some short-term relief to some limited areas of the state.
I have been scouting and participating in Extension programs in south central Kansas this week including Barber, Harper, Kingman, Pratt, and Reno counties. I found no leaf rust or stripe rust in these demonstration plots. Powdery mildew has been absent this year. I found trace levels of tan spot in a few fields on lower leaves. Other reports from Cheyenne, Jefferson, Nemaha, Osage Phillips, Saline, Sedgwick, Sherman, Sumner, Wallace counties indicate no disease in other areas of the state.
The risk of severe disease in Kansas remains very low this year.

-Erick De Wolf, K-State Extension Plant Pathology

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Wheat Disease Update (April 25, 2014)

A note from Jeanne: There has been no rust (stripe, leaf or stem) found in Cheyenne, Sherman, or Wallace counties as of April 25.

The risk of severe leaf diseases remains low throughout Kansas. My own scouting and reports from K-State agronomists indicate that leaf rust and stripe rust are not present in the state. Tan spot, septoria, leaf blotch, and powdery mildew were absent in most fields; however, we did find a small number of fields with low levels of tan spot in Saline, McPherson, and Sedgewick counties. These fields all had wheat residue from previous crops on the soil surface. This residue is important because it often harbors the fungus that causes tan spot.

Drought stress was evident in most fields and the dry conditions are holding disease in check for now. Recent rains have brought some temporary relief to the dry conditions in a few areas of the state. We will continue monitoring the disease situation as this moisture may stimulate some disease. The symptoms of any new infections would not become evident for 7-10 days. The current risk of severe disease in Kansas and the need for foliar fungicides is low.

Riskmap_2014

Summary of disease conditions in other states:

Texas has reported some stripe rust activity just south of Dallas but warm temperatures have slowed the progress of that disease. Bob Bowden, USDA Plant Pathologist, reports that leaf rust remains active in research plots near San Antonio, Texas. However, the disease remains at low levels in commercial fields according to Tom Isakeit, Extension Plant Pathologist for Texas A&M. Wheat fields in southern Texas are nearly ready for harvest. The trace levels of rust reported in central Texas have not advanced to cause problems in that area according to Ron French, Extension Plant Pathologist for Texas A&M. Rust has not spread into key wheat production areas of northern Texas.

In Oklahoma, Bob Hunger, Extension Plant Pathologist for OSU, indicates that leaf rust and stripe rust have not been found in Oklahoma yet this season. Conditions remain dry in Oklahoma and they are currently evaluating fields for evidence of freeze injury that occurred on April 15.

-Erick De Wolf, K-State Extension Plant Pathology

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Wheat Disease Update (April 10, 2014)

The growth stage of wheat in Kansas ranges from tillering in the northwest to jointing in the southeast and south central regions of the state. The development of the crop is 2-3 weeks behind schedule for this time of year. Dry soil conditions and thin stands continue to threaten yield potential and remain the primary concern for many wheat growers in Kansas.

Wheat leaf rust and stripe rust update

There are no reports of leaf rust, stripe rust, or stem rust to date in Kansas (figure below). Dry conditions appear to be holding rust and other fungal diseases in check in Kansas for now. Wheat soilborne mosaic was reported in a few fields in south central Kansas and in research plots near Manhattan. The symptoms of this disease often fade quickly as temperatures warm. Only trace levels of powdery mildew and tan spot have been reported to date in Kansas.

Riskmap_2012

Reports from other states

Oklahoma. Bob Hunger, Extension plant pathologist for Oklahoma State University, reports that rust has not been reported in Oklahoma to date. He reports that low levels of powdery mildew and tan spot were present in some fields.

Texas. In Texas, Amir Ibrahim, Texas A&M wheat breeder, reports that leaf rust and stripe rust continued to develop in irrigated research plots near San Antonio. He noted that the races of stripe rust able to overcome the Yr17 resistance present in many varieties with a Jagger pedigree (Fuller, Overly, Jagalene, PostRock) were rare to absent. Ron French, Texas A&M Extension plant pathologist, reports that rust was not present in commercial fields in north central Texas. However, he mentioned that stripe rust and leaf rust were present in commercial wheat fields south of Dallas in Waxahachie (Ellis County) and in Bastrop and Travis counties, which are east of Austin. He reports that Greer and Cedar were being affected by leaf rust. French indicates that temperature and moisture conditions in the Texas High Plains are not conducive for major disease epidemic.
Take home message

The current status of disease and dry weather suggests the risk of severe fungal diseases is currently low in Kansas. Clearly, the crop has a long way to go at this time. The delayed growth and development of the crop may increase the chances that leaf rust could arrive in time to cause damage.
Producers should keep an eye on what is happening in Texas and Oklahoma. Locally, producers should be checking their fields for symptoms of disease more frequently as the crop approaches flag leaf emergence.

-Erick De Wolf, K-State Extension Plant Pathology

Wheat Disease Update (March 31,2014)

This is just a quick update on the wheat disease situation in Kansas. All remains quiet in Kansas and I think winter kill and lack of moisture remain the primary issue on growers' minds.

There was an update from Texas late last week that we should discuss. This report indicates that stripe rust has increased in some research plots near San Antonio, but that they were expecting the progress of the disease to slow because of warmer temps in Texas. They were reporting disease on TAM 111, which suggests that the 2012 races were present (able to cause disease on Everest, Armour, and TAM 111). Leaf rust was also present, but appears to be restricted to the lower canopy at this point.

Oklahoma has not reported rust so far in 2014 and is concerned about drought and brown wheat mite.

My take on this is that the risk of severe disease in Kansas is still low.

-Erick De Wolf, K-State Extension Plant Pathologist

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Outlook for Wheat Rust in Kansas

Here is the projection of the risk of leaf rust and stripe rust in KS for 2014 based reports of disease and weather information throughout the Southern Great Plains to date.

Regional reports of disease: The years with several leaf rust and stripe rust epidemics in Kansas are often preceded by outbreaks of disease in Texas and Oklahoma. The first indications of problems often occur in Texas during February and March. So far, our colleagues in Texas and Oklahoma are reporting that leaf rust and stripe rust are absent or at low levels relative to recent years. However, there are a few spots in Texas that we will want to keep an eye on. Below are a few highlights.

Amir Ibrahim, wheat breeder for Texas A&M, reported both leaf rust and stripe rust in susceptible varieties in this irrigated field near San Antonio. This report indicates leaf rust has been slower to develop at this location than in previous years. A single focus of stripe rust was also reported at this location.
Tom Isakeit, Extension Plant Pathologist for Texas A&M, shared an unconfirmed report of leaf rust and stripe rust near Warton, TX (about an hour South of Houston). Tom indicates that this area of TX has little commercial wheat production. The isolation of this field may reduce risk of disease spread. Amir and Tom both indicate that wheat was ranged from late jointing through flag leaf emergence stages of growth.
Charlie Rush and Ron French, Texas A&M Amarillo, indicate that dry conditions still dominate in the panhandle region of TX and that there are no reports of rust to date.
Bob Hunger, Oklahoma State Univ. wheat pathologist, indicates that there are no reports of rust in OK so far this season, and that cold, dry weather conditions have not favored foliar diseases in OK.

In Kansas, the wheat has been emerging from winter dormancy over the past two weeks. There have been no reports of leaf rust or stripe rust so far in 2014. As you may recall, leaf rust was reported last fall near Manhattan, KS. I revisited these fields today and was unable to find the disease suggesting tha the leaf rust did not overwinter. In recent weeks, I also visited fields near Garden City (SW Kansas), Great Bend and Hutchinson (both in central Kansas). There was no evidence of disease in the fields I checked.

Assessment based on weather: Researchers here at KSU have been evaluating the weather conditions associated with historic epidemics of stripe rust in Kansas. This research indicates that stripe rust epidemics are most likely to occur when regional moisture conditions favor disease development in the fall (Oct-Dec) and winter months (Feb). Based on regional moisture in the fall and winter months in 2013-2014, it appears that the risk of severe stripe rust is low for Kansas.

The bottom line: My current evaluation of the regional disease reports and weather patterns indicate that the risk of severe leaf rust and stripe rust in KS is low. I will provide regular updates about the status of disease as the season progresses. So stay tuned, because disease situations can change rapidly.

-Erick DeWolf, Extension Plant Pathologist, Kansas State University

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Stripe Rust Update (5/11/13)

The wheat is heading and flowering in southeastern and south central Kansas this week. Wheat in central Kansas is mostly in the boot stages of development with the most advanced fields beginning to head this weekend. The wheat in southwestern KS continues to struggle with drought and freeze damage and growth stage varies widely among fields.

Disease scouting this week suggests the risk of severe rust epidemics remains low in Kansas this year. I had a few more reports of trace levels of stripe rust in southeastern KS where the wheat is flowering. The levels of stripe rust are very low at this time. Temperatures are forecast to reach the upper 80's early next week with low temps at or above 60 F. Temperatures in this range often slow the development of stripe rust but farmers in these areas should monitor the disease carefully.

I was able to find a single pustule of leaf rust in Stafford county Kansas this week, but the wheat at this location was thin from recent dry conditions. I suspect the leaf rust will not increase rapidly at this location. Other fields that I checked in southwest KS (Finney and Kiowa counties) show significant drought stress and no sign of rust. In south central and central Kansas (Pratt, Reno, and McPherson counties), the wheat is in better condition with thick canopies and good moisture recently. I found no leaf rust, stripe rust or stem rust in these areas; however, several fields had moderate levels of powdery mildew. Symptoms of barley yellow dwarf remain low or absent in all fields I have checked to date.

-Erick De Wolf, Kansas State University Extension Plant Pathologist

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2013 Wheat Disease Update

Early Season Wheat Disease Update for Kansas (3/22/13):

March is an important month for wheat disease development in Kansas. This statement may surprise some of you, because the wheat is only just greening up in some areas of the state.

As it turns out, February and March are important because we often receive our first reports of disease activity from states to our south. This is particularly relevant for the rust diseases, which often survive the winter in these southern climates.

So far this year there are several reports of rust developing in Texas, Arkansas, Louisiana, and Mississippi. Stripe rust has been observed in all four states and appears to be spreading beyond the initial foci of infection. Leaf rust has been reported in Texas but not the other states.

The reports of stripe rust and leaf rust from Texas are the most important for us, because weather systems often transport the rust spores from these regions into Oklahoma and Kansas. Varieties such as Everest, Armour, and TAM 111 are being affected in Texas this year. This is similar to what was observed in 2012 and there are no reports of new races of stripe rust to date.

Bob Hunger, wheat disease specialist for Oklahoma State University, is reporting no finds of rust in Oklahoma as of March 21. Growers in Kansas should be monitoring the situation in Texas and Oklahoma. If the disease continues to develop in Texas or is reported in Oklahoma, we will need to evaluate the need for fungicides to suppress rust development in fields planted to susceptible varieties.

-Erick DeWolf, K-State Wheat Pathologist

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Texas (12 mi west of San Antonio) (3/7/13): I toured our rust evaluation nursery located 12 miles west of San Antonio, TX on March 07, 2013. The crop stage varies from Feekes 4 to 10.5 depending on growth habit and source. The wheat crop is early by at least two weeks compared to long term average (spring and winter wheat).
Leaf Rust is also developing uniformly in the lower to mid canopy of 'TAM 110'. Consistent with previous years, there is more leaf rust in the observation head-rows as compared to the yield trials.
Stripe/yellow rust (Yr) is still developing in the lower to mid canopy of the spreaders, including 'Patton'. Both Lr and Yr (30S) are present on the same leaves of 'TAM 112'.

No indication of a leaf or yellow rust race change but it is early to tell at this point.

-Amir Ibrahim (Texas A&M small grains breeder)

Oklahoma (2/26/2013): Although still no confirmed reports of foliar disease in Oklahoma wheat, the recent moisture will facilitate foliar disease development as temperatures raise as we enter March. Symptoms of wheat soilborne mosaic/wheat spindle streak mosaic are evident in that disease nursery here at Stillwater and with the wet/cold weather of this and last week should become more prominent as we get into March.

Bob Hunger (OSU Extension Plant Pathologist)
Texas: Uvalde (West of San Antonio) (2/23/2013): The wheat crop is at Feekes 4-5. Leaf rust continues to develop uniformly at this location and is severe on susceptible cultivars such as "TAM 110". Stripe rust continues to develop but might be slowed by increasing temperatures at this location. It seems we have the same race that was virulent on "Everest" and "TAM 111" last year.

-Amir M.H. Ibrahim (Texas A&M Small Grains Breeder)

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Stripe Rust Update (May 2, 2012) and the Economic Threshold of Aphids

When spending time checking wheat during the last two days, I can see an increase of incidence of stripe rust. It is now showing up on flag leaf. This is especially evident on varieties that are showing the greatest susceptibility. These varieties include: TAM 111, Armour, Everest, TAM 112 and Jagalene. Some of the varieties that are still showing symptoms, but the development has been slower, are: Fuller, PostRock, Overley, Winterhawk, TAM 304, T-158 and Danby.

In addition, I looked at some irrigated wheat and was a bit surprised in the quick progression of the disease. This was in a susceptible variety that significantly increased in less than a week - progressed to the flag leaf and increased in severity in the mid canopy. The canopy has also been slow to dry out because of the foggy, moist, cool mornings and irrigation. This coupled with the cool overnight lows and moderate daytime temperatures.

A great deal of fungicide is being applied. It is important to note the preharvest intervals. Some of the popular fungicides being currently applied and their preharvest intervals are:

Folicur (active ingredient: Trebuconazol) - 30 days
Quilt and Quilt Xcel - full bloom
Prosaro - 30 days
Headline - full bloom

I have also been getting many questions about insecticides for aphids in wheat. Here is what I found for aphid thresholds.

Greenbugs: pale green with dark green stripe down back

Seedlings - 50 greenbugs/linear ft of row
3 to 6" wheat - 100 to 300 greenbugs/linear ft of row
6 to 10" wheat - 300 to 500 greenbugs/linear ft of row

Bird Cherry Oat Aphid: olive green colored

At boot to heading stage - 50+ per tiller

Russian Wheat Aphid: light green body

Around 20 bu/ac yield potential - 20% of tillers show symptoms and have live aphids
40 bu/ac + - 10% of tillers show symptoms and have live aphids

Stripe Rust Update (April 26, 2012)

Stripe rust is being detected in trace levels in Sherman County. While looking at the Sherman County wheat plot, I found one leaf with a trace level of stripe rust on it. This was in the variety Garrison and this variety is very susceptible to stripe rust. This was on FL-2. It was also in the very early stages of development. The three pustules still had the glossy look and were not actively releasing spores.

Stripe rust has also been found in trace levels in Cheyenne County. This was found on TAM 111 in a protected area of the field in the canopy (not on the flag leaf). It was also in preliminary stages of development and likely just emerged from the leaf surface in the last 24 hours.

This update, combined with the one from earlier this week shows that stripe rust has been positively confirmed in Thomas, Wallace, Sherman and Cheyenne Counties. I also have a stripe rust report in Decatur County near the Nebraska line, with rust on FL-2 and FL-1 in trace levels.

TAM 111 has been resistant to stripe rust, until 2012. This year, the rust overcame the single-gene of resistance and is now susceptible to stripe rust. Other varieties that we have preliminary determined to be quite susceptible are Armour, Everest and Garrison. In addition, basically all wheat varieties have some level of susceptibility this year.

Since, stripe rust is not located on the flag leaf, there is a question on the need to treat stripe rust. There are some important items that go into making that decision. Stripe rust loves moist and cool weather and thrives in these conditions. It has been thought that stripe rust would shut down at high daytime temperatures (like over 80°.) Upon further study, the nighttime temperatures have a greater effect. After 2-3 nights, with overnight lows above 60°, the stripe rust will shut down. In addition, stripe rust can incubate in the leaf for 2-3 weeks before erupting from the upper surface of the leaf.
2012 Fungicide Chart - this has information of fungicide treatments with preharvest intervals.

Stripe Rust Update (April 24, 2012)

After scouting fields in Thomas and Wallace Counties today, stripe rust has been found. This is being found in extremely trace levels and is not evident in every field that is walked into. See the attached pictures. No stripe rust was found on the flag leaf. All stripe rust pustules were located on one or two leaves below the flag leaf. In addition, this was nearly all located in lush wheat. I scouted this wheat first because it is wheat that would hold moisture the longest. Moisture is a key component for infection of stripe rust.

The pictures show the beginning of rust pustules on the leaf upper surface. These pustules are very newly emerged from the leaf surface, in the last 24-48 hours, and are not actively sporulating (releasing spores). The stage of releasing spores is when orange will appear on fingers after rubbing them across the leaf surface. This will happen over the next couple days. That is likely the period when the flag leaves will become infected. The stripe rust will incubate in the leaf after infection for 2-3 weeks before pustules will appear.

The weather over the next couple days will help determine control tactics on this disease. Stripe rust likes temperatures between 50 and 80°. Temperatures of 90 today will not be enough to stop the disease. It is actually night temperatures over 60° will stop stripe rust. In addition, the warm temperatures will increase stress on the wheat. Cooler temperatures and possible rain by the end of the week are favorable to stripe rust development.

In addition, 'flecks' on the leaf surface are not indicative of stripe rust. These flecks can be from a number of sources (mainly environmental) and are visible when holding the leaf up to the light. There is one variety, Hatcher, which responds to stripe rust with these flecks. However, in Hatcher, the flecks are elliptical shaped along leaf veins. The flecks that are visible now are randomly scattered on the leaf surface.

This 2012 Fungicide Chart has information on fungicide treatments, timing, rates and preharvest intervals. In addition, all fungicides have 2-3 weeks of residual activity. This depends on the stripe rust pressure and environmental conditions.

I will be scouting in Rawlins, Cheyenne and Sherman Counties tomorrow (Wednesday, April 25) and will send out another report tomorrow evening/Thursday morning. If you have any questions, please let me know.

Threat of Stripe Rust for Wheat (April 13, 2012)
From Jeanne Falk, K-State Multi-County Agronomist:
Stripe rust has been found in trace levels in southern Scott County. This is the closest stripe rust to the Sunflower District. The threat level for stripe rust in the next week is moderately low.

Moderate temperatures and heavy dew in the morning are two components needed for infection of stripe rust. Both of these components will be in place this week and can increase the risk for infection of stripe rust. The final component is the stripe rust innoculum. Since the presence of disease continues to move closer, the risk is increasing. Since there are only trace levels showing up in fields shows, the risk for an explosion of stripe rust (similar to 2010) is low at the current time.

Also remember that the flag leaf contributes over 75% of the nutrients for the filling of the wheat head. Do not apply prior to at least 2/3 flag leaf emergence. Fungicides have limited translocation in the plant. This means the fungicide can move a limited amount (less than 1/2 inch) in the leaf. It can not move leaf to leaf.

Please read Erick's information below about the change in the stripe rust to attack different varieties.

From Eric DeWolf, K-State Wheat Pathologist:
The wheat in Kansas is now heading and beginning to flower in Southeast and South Central Kansas. Wheat in central KS is now at the boot stage and will likely begin to head soon. In fact, it is likely that some fields are already beginning to head out in central region of the state. As we move north and west in the state, the wheat is moving toward flag leaf emergence to boot stages of development.

My own scouting and reports from other KSU agronomists and agents indicates that stripe is generally at low levels in many fields throughout central Kansas. The stripe rust was generally limited to the F-2 and F-1 leaves and less than 1% incidence. This afternoon; however, I have received reports that stripe rust has now moved to the flag leaf and the severity of disease has increased dramatically in some fields. Here are some specific reports: Stripe rust was reported on the flag leaf in Montgomery, Labette, Crawford and Wilson counties (Southeast, KS). Stripe rust was reported on the upper canopy (F-1 and Flag) with a noted increase in the incidence in many fields this past week in Saline, McPherson, Harvey, Reno and Ellsworth county (central KS). Stripe rust was observed on the flag leaf in Sedgwick county (South central, KS) with severe stripe rust developing in a field of Armour wheat in the southeast portion of this county. I have also seen stripe rust in north central KS including Cloud, Mitchell counties. The disease appears to be limited to the F-2 and F-1 leaves currently in north central KS.

Varieties with the Jagger based pedigree that have Yr17 are being affected by stripe rust. Varieties such as Everest, Armour, and TAM111 are also being affected by stripe rust this year. This strongly suggests that the stripe rust population has changed to overcome these sources of genetic resistance.

My assessment of the situation is that stripe rust is widely established in central Kansas this year. The weather has been conducive for disease development and the weather forecast appears to favor continued development. The disease is still at low levels in many fields, however, the severity of disease will likely increase dramatically in the next 10 days. I think there is high risk of severe yield loss to stripe rust for wheat in at least the eastern 2/3 of Kansas. Based on my current information I believe there is at least a moderate risk of severe disease in western KS. I will attempt to get more information about western Kansas next week.

Threat of Stripe Rust for Wheat (April 6, 2012)

Stripe rust is a challenging wheat disease because it thrives in the same environment that wheat thrives. These conditions include moderate temperatures with moisture.

The following is a report from Erick DeWolf, K-State wheat pathologist. "I continue to get reports of low levels of stripe and leaf rust in Kansas. Reports to date have come from primarily south central and central regions of the state. Counties where stripe rust has been reported include: Harper, Kingman, Sedgwick, Pratt, Reno (south central); McPherson, Saline (Central). The wheat in these areas of the state ranges from flag leaf emergence to heading, which is approximately 2-3 weeks ahead of normal crop development. Weather conditions this week have been favorable for continued spread and development of rust diseases."
With the storms that moved through the area in the last couple weeks, they circulated in a counter-clockwise direction. This could move rust spores from central Kansas to western Kansas. This is a bit of a deviation from the normal south to north movement of the rust spores on the wind currents. There have also been reports of trace levels of rust in the panhandles of Texas and Oklahoma. These are usually the areas that are watched for the movement of stripe rust into northwest Kansas.

Finally, this is just an early warning and is not a cause for alarm. It is just important that everyone know where we are with this disease. Our wheat is not in the stage of growth for fungicide applications to protect from rust. Wheat is normally treated when the flag leaf is at least 2/3 emerged. This is because fungicides move only on a limited basis within a leaf and will not move from leaf to leaf in the plant.

If you have any questions, please call me at the K-State Extension Office or at the Experiment Station in Colby at (785) 462-6281.

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Are Viruses Always Found in Volunteer Wheat?

Last fall, volunteer wheat fields were sampled in Sherman and Cheyenne Counties to determine the level of wheat virus infections. The wheat was tested for Wheat Streak Mosaic, High Plains Mosaic and Triticum Mosaic and a combination of these. Erick DeWolf, K-State Wheat Pathologist and I randomly selected these volunteer wheat fields.

Each of these viruses are vectored by the wheat curl mite and can be moved from volunteer wheat into planted wheat fields. Spring infections of these viruses tend to have less impact on yield when compared to fall infections.

Cheyenne County

Triticum Mosaic 3.1%
Wheat Streak Mosaic 28.1%
High Plains Mosaic 31.2%
Triticum + Wheat Streak 6.3%
Wheat Streak + High Plains 3.1%
66% of plants were infected with a wheat virus. 32 plants were sampled.

Sherman County
Triticum Mosaic 0%
Wheat Streak Mosaic 9.8%
High Plains Mosaic 9.8%
Triticum + Wheat Streak 2.7%
Wheat Streak + High Plains 17.1%
39% of plants were infected with a wheat virus. 41 plants were sampled.

The combination was tested for because individually, these viruses can have impacts on yield. However, when these are put in combination the yield effects can be catastrophic.

When identifying these viruses, they all look very similar. They all have the mottled yellow streaks that are concentrated on the leaf tips. As the leaves become progressively more yellow with time, the leaf veins will often retain a greener color. Therefore, the determine the virus that is causing the symptoms, a plant sample should be sent into the plant pathology lab at K-State.

There is no cure for viruses in wheat. These are likened to the flu in humans. Healthy wheat (not lacking on fertilizer, drought stressed, etc) will generally fight the virus longer without seeing symptoms and will have less yield loss than wheat that has poorer health. The best cure for wheat viruses is prevention. Controlling volunteer wheat is a great prevention option.

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