Unfortunately, it appears that one of the most common problems for wheat producers this year is not a weed or other pest, but the occurrence of glyphosate drift. Damage reports first started coming in from the southern counties over two weeks ago, as wheat begins to head further north reports from county agents are coming in like a roll call from south to north. I cannot begin to estimate the number of acres affected at this time, from my cell phone it seems like all of them.
If you are familiar about glyphosate drift on rice, you know the effects of glyphosate drift to wheat. During tillering effects of small amounts of glyphosate on wheat can cause stunting, chlorosis and some dead leaves and tillers; however, prior to jointing this damage does not effect seedhead or flagleaf development. If drift, even in small amounts, occurs after tillering and after joint formation begins (like green-ring in rice), the damage is basically invisible until the flagleaf emerges. Flag leaves will be stunted (a symptom of almost no other ailment in wheat), bleached to striped white or yellow chlorosis, often twisted at the base of the flagleaf where it attaches the stem. If the flag leaf is damaged, a damaged head almost always follows. This can resemble the effects of late applications of 2,4-D as seedheads get “caught” in the collar region and can emerge sideways from the sheath. There is no cure for glyphosate drift damage and damage can range from 5-100% depending on severity of injury, which depends on rate and timing. It is proving difficult to find the source for many of these drift calls.
If you suspect that you have field damage due to drift, please contact the Arkansas State Plant Board at (501) 225-1598.