Fomesafen is an active ingredient found in many popular herbicides labeled for soybeans, which include Flexstar GT, Warrant Ultra and Marvel. Fomesafen has proven to be an effective herbicide to assist in control of pigweed species including waterhemp and palmer amaranth. With increased performance on tough to kill weeds also comes potential risk of injury to your rotational crop the following season. Fomesafen carryover injury on corn will appear as streaking of the leaf veins on the first few of leaves of young plants. Usually plants will continue to grow without prolonged injury, but in rare cases, stand loss can occur. It is extremely rare to have yield reduction because of fomesafen carryover.
Fomesafen carryover is mostly likely to occur when applications are made after June or when rainfall becomes limited after application. Fomesafen has a 10-month rotational interval for corn, so applications must be made no later than mid-late June. The use of fomesafen is restricted for counties west of Highway 281 in Nebraska.
This week, Norder Supply Agronomists have identified cases of Fomesafen carryover injury to corn. Rainfall has been less than average in our area since June of 2017 applications. This coupled with a cool few days last weekend is why the symptoms have started to appear. The cool weather slows the growth of the corn plants and they struggle to metabolize the small dosage of fomesafen still present from last season’s application. After a few days of sunny weather, we are already seeing plants recover, and except for a few rare cases, no long-term effects are expected.