Fomesafen Carryover to Corn
ISU Extension and Outreach Field Agronomists recently highlighted a significant number of phone calls related to fomesafen carryover injury to corn rotated from 2020 soybeans.
ISU Extension and Outreach Field Agronomists recently highlighted a significant number of phone calls related to fomesafen carryover injury to corn rotated from 2020 soybeans.
There have been a few fields where topramezone – the active ingredient in Impact and Armezon – carried over from an application last June – and is injuring this year’s soybean crop. Other agronomists have reported carryover of other Group 27 herbicides on soybean this year (mesotrione, isoxaflutole).
This was observed this in 2013, but it did not affect a lot of acres that year. However, that was following the drought year of 2012 and the lack of summer rainfall in 2012 somewhat explained this problem.
Although there is no evidence of widescale problems with carryover injury to corn or soybean, ISUEO field agronomists have received a few reports. The potential for carryover injury is determined by several factors, including: 1) persistence of the herbicide, 2) herbicide rate, 3) soil characteristics, 4) amount of rainfall during the season following the application, 5) length of interval between herbicide application and planting the rotational crop, 6) sensitivity of the crop to the herbicide, and 7) early-season crop vigor.
ISU Extension and Outreach Field Agronomists continue to receive calls regarding fomesafen carryover injury to rotational corn. There are several factors resulting in this injury: 1) continued problems with waterhemp result in late-season applications, 2) fomesafen is relatively persistent, and 3) many areas of Iowa received less than average late-season rainfall in 2017. In most cases, this carryover injury has been limited to relatively small sprayer overlap areas, though some fields are showing injury on a more widespread area.
Reduced herbicide degradation is one of the consequences of the current drought. It could lead to damage in rotational crops next spring. The risk of carryover injury will vary widely from field to field, making it important to evaluate each field individually.