Wheat Disease Update April 7, 2017
Wheat growth is progressing at a steady pace, with most fields in the state looking green (Figure 1) with little or no disease. At UNL’s Havelock Farm in Lincoln (Lancaster County) on April 6, wheat growth stage was mostly at early jointing with the first node detectable (Feekes 6). Examination of the lower canopy in research plots revealed powdery mildew (Figure 2) and fungal leaf spots (Figure 3). These observations indicate that disease is starting to develop in wheat fields.
To date there have been no reports of stripe rust or leaf rust in Nebraska or Colorado. Stripe rust was reported in southeast Kansas on April 4. This is the first report of stripe rust in Kansas this growing season. Stripe rust was reported in Oklahoma in late March, but it was not widespread. As of April 4, development of leaf rust was picking up in Oklahoma, along with powdery mildew.
Scouting should continue at regular intervals for early disease detection. (See the March 24 CropWatch story, Start Scouting for Wheat Diseases.) Because of the current and forecasted wet weather, wheat diseases are expected to develop to severe levels.
Fungicide sprays should be aimed at protecting the flag leaf. However, if disease is seen to be developing to severe levels early in the growing season, a pre-flag leaf fungicide spay may be warranted. Base the decision to spray early in the season on the presence and level of disease in the field. If stripe rust is detected, spraying is advised because the current weather is favorable to its rapid development and spread once present in the field.