Wheat Disease Update Archives
Helpful Resource for Rust Diseases: Identifying Rust Diseases in Wheat and Barley
I checked wheat yesterday and began finding stripe rust and scattered leaf rust pustules in Sherman, Thomas and Cheyenne Counties. This is in addition to finding both stripe and leaf rust in Wallace County on Monday. I am finding the rust on 1 and 2 leaves below the flag leaf (FL-1 and FL-2). Even though I can find both of these fungal diseases, I am spending quite a bit of time looking in the most susceptible varieties. And the pustules are just emerging from the leaf surface in the susceptible varieties. I have not found rust in the more resistant varieties, but I haven’t spent quite a much time scouting in those varieties. In addition, since the pustules are just emerging, there is very little orange is wiping off the leaf onto your thumb or finger. Therefore, it is important to look for a rust pustule ‘bump’ on the leaf. To see this roll the leaf over your finger against the light to see if there is a bump on the leaf surface.
I put together this graphic shows the progression of stripe rust (and some of the different stages that you are seeing in the field):
So, now is the time for making fungicide decisions in far northwest Kansas. I would prioritize the fields with the most susceptible varieties. Those include Avery, Byrd, Brawl CL, and Denali. These are rated 7 and 8 (on the 1 – 9 scale with 1=resistant and 9=susceptible). Look up your variety rating with the K-State Wheat Disease and Insect Ratings publication: https://www.bookstore.ksre.ksu.edu/pubs/MF991.pdf
Many fungicides provide very good to excellent control of both the stripe rust and leaf rust. Here is the publication outlining the efficacy of many fungicides for several wheat diseases (including stripe rust and leaf rust): https://www.bookstore.ksre.ksu.edu/pubs/EP130.pdf
With the weather forecast, it is going to be difficult to get into the field to apply your own fungicide. However, you if you are able to get into the field between rain showers, be sure to check the rainfast period for the product you are applying. For many of the generic tebuconazol products, the label says it must have 2-4 hours of drying time before rain or irrigation. It is different for other fungicides, so be sure to check the label of the product you are applying.
Here is a 7 minute video that I recorded in the field last night discussing the stripe rust and leaf rust (and where to look on the plant when you are scouting wheat): https://www.facebook.com/kstatesunflowerdistrict.agronomy/videos/430871794410295/
If you have any questions on what I am finding in the field, please let me know. Thank you to everyone who has been scouting for wheat rusts and letting me know what they are finding! I really appreciate the group effort in scouting!
I looked at wheat yesterday and found stripe rust in Wallace County. It was in a susceptible variety, Avery. Avery is rated an 8, on a 1 to 9 scale with 1=highly resistant and 9=highly susceptible. It was located on the leaf below the flag leaf (FL-1) and was very challenging to find.