Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
Vol. 11, No. 12
Mar 16, 2012
Wheat Disease Update
Bob Hunger, Extension Wheat Pathologist
Although not severe, powdery mildew (PM) can be found with ease in most trials on susceptible varieties if the growth is thick. Weather this week was favorable for wheat growth and disease development with highs between 75-85°F, lows in the mid-60s °F, and with high humidity and dew formation most mornings. This should lead to a dramatic increase in PM levels and also provides favorable conditions for leaf rust; it actually may be a little warm for stripe rust (one day this past week reached 88°F!). Our early foliar fungicide application was done on 14-Mar at GS 7. Two nodes were easy to find on most tillers with emergence of the flag leaf not all that far away on some tillers (variety is Jagger). Still no leaf rust observed this far north in Oklahoma, but observation of sparse pustules were reported to me last week by Gary Strickland (Extension Educator, Jackson County – SW Oklahoma). Septoria is evident on lower leaves but is not severe. Soilborne-spindle streak symptoms are disappearing quickly in that nursery. As indicated below and also confirmed by other Extension Educators around the state, aphids are abundant. I have seen both bird cherry oat aphids and greenbug around Stillwater. Symptoms of BYD continue to develop.
Dr. Jeff Edwards (OSU Small Grains Extension Specialist) reported on 15-Mar, “I did not see much disease at all. I saw just a little PM at McLoud (just east of Oklahoma City) in wheat that should have been loaded with it. Plenty of aphids, though!