Temperatures at our winter wheat variety testing sites (Janesville, Arlington, Lancaster, and Chilton) ranged from the mid 30’s to the high 40’s in the early morning hours of June 1st. Though these temperatures are generally not low enough to cause yield loss we are hearing initial reports of wheat heads being caught in the boot or in the extreme being tangled in the flag leaf (Images 1 and 2). This symptomology is most prone in awnletted wheat varieties (varieties with very short awns), but can also occur to awned wheat. If wheat heads are merely bent then yield loss is unlikely however if wheat heads are completely snapped off then yield loss has occured and growers should contact their crop insurance agent.
If entire fields are showing uniform injury or patterns appear check spray records and timings to ensure that head damage is environmetnal and not herbicidal as growth regulator herbicides such as dicamba and 2,4-D can cause epinasty (twisting) and head malformation.