Stripe rust has arrived in the wheat!

Sandra Wick, Crop Production Agent

Well, the wheat crop is well ahead in its growth and development for this time of year and producers should be scouting for diseases that are showing up in all parts of the state.

So what does this mean for wheat growers in Kansas? The early reports of stripe rust and some leaf rust are cause for concern as the risk of disease outbreaks and disease-related yield loss increases dramatically when the rust becomes established in the state prior to heading according to Dr. Erick DeWolf, K-State Research and Extension plant pathologist.  There are reports of increasing disease in southern and central Kansas with stripe rust along with fields in northcentral Kansas.   If weather conditions are right, the disease may move into more fields.  Recently, I scouted several wheat fields in NC Kansas and did find stripe rust and in all counties, of the Post Rock District, in some degree depending on the variety.  But mostly on the lower canopy of the wheat plants.

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 certainly help determine critical decisions about fungicides. Checking wheat varieties reaction to rust can help growers set priorities for scouting. Everest is widely planted in most areas of the state and is susceptible to stripe rust and should be monitored carefully for symptoms of stripe rust. However, there are varieties that are also grown that have resistance such as KSU 1863 and Grainfield along with LCS Mint and KanMark.  K-State Research and Extension has an excellent publication, “Wheat Variety Disease and Insect Ratings for 2015” that will provide ratings for disease resistance or susceptibility of many Kansas wheat varieties.  This is available online or at your local Extension Office.  There is also a KSU Fact Sheet available, “Wheat Stripe Rust” at the following website http://bit.ly/20ObKlO and at your local Extension Office.

Producers should begin to gather information about fungicide options as there are excellent products available. However, the price of these products and applications will be particularly important this year, because the value of wheat is lower compared to some recent years.

So what does this mean for spraying a fungicide?  Do NOT get in a big hurry to spray a fungicide application.  

Stripe Rust in Headed Wheat

The timing of these applications is also very important.   KSU research has shown that a single fungicide application applied between boot and flowering stages of development results in the maximum yield benefit, thus protecting the flag leaf which is your primary concern. Fungicide applications made prior to jointing, followed by a second application may also be an option. However, 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, especially the flag leaf.   The efficacy or residual for most fungicides is 21 days. 

So it is a wait and see game.  It may be that the "right" conditions will not happen to enable the stripe rust to continue to develop.  Moisture and temperature are key factors.  Rainfall isn't always needed to stimulate rust growth, simply dew can do the same.  Daytime temperatures of 60-70 degrees F. and night time temperatures above freezing enable the rust to continue to develop.  For further information on disease management in your wheat, contact me at any Post Rock Extension District Office in Beloit, Lincoln, Mankato, Osborne or Smith Center.