It’s late April and the wheat crop is barreling into the flag leaf growth stages in many parts of the state. The rainy weather over the last week has growers wondering what the stripe rust outlook is now going forward. Some producers are likely considering the need for a flag leaf fungicide application. The good news is that, even though we’ve received some moisture, the risk for stripe rust in the state remains low, says Kelsey-Anderson Onofre, K-State Extension Plant Pathologist. Scouting efforts should continue over the next two weeks. In this article, Kelsey will walk through some of the reasons for the current low stripe rust risk and other diseases to be thinking about in wheat right now.
The risk of stripe rust in Kansas remains low for 2025 - on March 27, K-State reported that it was shaping up to be a low stripe rust year in Kansas. That trend still appears to be holding true. Stripe rust has been active at low levels in Texas since February, but conditions have not been favorable for disease development. This is important because stripe rust does not survive the winter in Kansas and needs to work its way up from the south annually. Low disease pressure in Texas means fewer spores are available to make their way north to Kansas. Additionally, at the time of this report, only trace levels of stripe rust were reported in Oklahoma. The first stripe rust detection in Kansas was recently reported on April 28 in Ford County. For reference, in years when stripe rust is an issue, it is generally detected in Kansas before April 15. With all of this in mind, we believe it will be difficult for stripe rust to establish and “catch up” at this point in the season, says Kelsey. Because of this, the risk of stripe rust remains low in the state. As a reminder, the probability of a positive return on a fungicide application greatly diminishes when disease pressure is absent. That said, producers should continue to scout and report any occurrences through the remainder of the season. These next two weeks will be critical for much of the state.
Should growers be worried about leaf rust? Reports from Texas indicate that leaf rust is active. As a reminder, leaf rust is a disease that typically shows up late in the season in Kansas (heading to flowering) due to its preference for slightly warmer temperatures. It is possible for leaf rust to occasionally survive the winter in Kansas. Watching for leaf rust development over the next few weeks will be important. Now is also a good time to check your variety resistance level to this disease, google “KS. Wheat Variety Guide 2024”.
Let’s turn our attention to the scab risk over the coming weeks - wheat fields planted into corn residue are at the highest risk. Wet weather over the next couple of weeks will be critical for determining scab risk in the state. As a reminder, scab infection occurs at flowering, but symptoms are often not visible for 14-21 days after infection. Because of this, you cannot scout for scab the way you would stripe rust or other foliar diseases. Fungicide decisions need to be made according to weather-based risk and the field’s yield potential. However, if wheat was not planted into corn residue, your risk of scab is low.
Fungicides are most effective against scab when applied at early flowering (Feekes 10.5.1), but can provide protection even when used later in the flowering window. It is very important to pay attention to pre-harvest intervals at this point of the season and follow guidelines provided on product labels.
Information provided by Kelsey Andersen Onofre, Extension Plant Pathologist.
Stacy Campbell is an Agriculture and Natural Resources agent for Cottonwood Extension District. Email him at scampbel@ksu.edu or call the Hays office, 785-628-9430.
