Some wheat disease observations in the past week
Despite powdery mildew, common leaf rust and barley yellow dwarf virus visible in research plots, the wheat crop in Michigan looks promising.
Martin Nagelkirk and I toured the Thumb last week with a group of agronomists from Kellogs and Star of the West and had the opportunity to observe some diseases developing in research plots. There was not much developing except some Stagonospora leaf blotch (Stagonospora nodorum) and in the plots at Clarksville there was also abundant powdery mildew (Erisyphe graminis; Photo 1) and the beginning of common leaf rust (Puccinia triticina; Photo 2).
In one of our fungicide trials at Dewitt, there were also the beginnings of Fusarium head scab in the plots at low incidence and severity. Armyworm larvae were fairly abundant as were aphids in some crops and plots and in some plots flag leaves were showing symptoms typical of barley yellow dwarf virus (BYDV). Barley yellow dwarf virus is caused by a group of luteoviruses and are transmitted by various species of aphid. Symptoms caused by BYDV can be confused with nutritional disorders and include leaf discoloration from the leaf tip to the base and from the margin to the centre. Wheat leaves generally turn yellow but sometimes turn reddish-purple (Photo 3) and may corkscrew. Plants may be stunted and have a reduction in tiller number reduced root system. In severe cases, yield loss can be as much as 10 percent. In the fields observed in our tour, there were only a few plants showing symptoms and yield would unlikely be affected.
In general, the wheat crops looked to be in good health and the majority had been treated once or twice with fungicides and an insecticide. There was also some evidence of damage (yellowing to browning) on the margins of the upper leaves from applications, possibly of mixtures of fungicides with NIS, insecticide and fertilizer. The general consensus of the tour group from Kellogs and Star of the West was that despite the wet spring, the wheat crop in Michigan looked promising.
Dr. Kirk’s work is funded in part by MSU‘s AgBioResearch.