Drought, freeze damage and stripe rust plague 2020 wheat crop

Posted May 14, 2020

Total precipitation received across Kansas during the 2020 wheat growing season is anywhere from five inches below normal to close to normal in central and western Kansas. These numbers indicate that severe, long-term drought stress has been established in parts of the state. Meanwhile, a more short-term analysis (January 1, 2020 to present) suggests that the region mostly affected by winter and spring drought is north central Kansas, which is up to four inches behind in precipitation accumulation for the period.

Several wheat fields in north central Kansas and the western third of the state are showing symptoms of short-term drought stress, including leaf rolling and loss of older (lower) leaves and a blue canopy coloration. These symptoms are sometimes coupled with damage from the recent freeze events which causes abortion of older leaves and yellowing of lower canopy to be more pronounced.

In western Kansas, many fields are showing long-term symptoms of drought stress, including extremely reduced plant height and maturity acceleration. Many of the fields are achieving later stages of development at only 9-15 inches tall due to the prolonged stress. The lack of growth will not only reduce the crop’s yield potential, but also create difficulty during harvest. The combination of a severe fall drought in southwest Kansas, followed by freeze damage on April 13 plus spring drought, has led many southwest Kansas growers to abandon their wheat fields and terminate them to plant a summer crop.

Read More: Drought stress taking its toll on Kansas wheat production in 2020

In addition to drought and freeze damage, several new occurrences of stripe rust have been reported in the last couple weeks.

So far, incidence has generally been low (about 1%), and reports have been limited to the lower-to-mid canopy. There is evidence that disease incidence is increasing at some locations and producers should continue scouting efforts. Lower canopy infections are less likely to result in yield reductions. When environmental conditions are favorable (extended periods of dew, for example), infections in the lower leaves may spread to the upper canopy and neighboring plants, resulting in reduced yield. Spread within a field and symptoms that have moved to the upper canopy may warrant a fungicide application. To preserve yield, it is critical to protect the flag leaf.

Stripe rust presents with characteristic yellow lesions that form in narrow bands across the leaf. When conditions are right, spores may spread to and infect the upper canopy. It is important to walk into the field during scouting campaigns and to move the canopy aside to get a good view of lower leaves. Walking several parts of the field is a good idea, as stripe rust can be easy to miss from the edge of the field.

If you find stripe rust in your county, please send a report to your local extension agent or directly to Kelsey Andersen Onofre (andersenkf@ksu.edu) and Erick DeWolf (dewolf1@ksu.edu) with photos of symptoms, if possible.

Additional information for fungicide decision making can be found in the publication Evaluating the Need for Wheat Foliar Fungicides (https://bookstore.ksre.ksu.edu/pubs/MF3057.pdf) and information on product efficacy can be found in the Foliar Fungicide Efficacy for Wheat Disease Management publication (https://bookstore.ksre.ksu.edu/pubs/EP130.pdf).

Read More: Reports of stripe rust are increasing across Kansas, although incidence remains low