Commercial Safened ALS‐herbicide Formulation Effects on ALS‐sensitive Field Corn Hybrids

Abstract

Core Ideas Corn hybrid sensitivity to ALS herbicides is an issue. Herbicide safeners may not provide complete crop safety. Growers who want to use safened ALS herbicides on sensitive corn hybrids must be aware of yield loss potential. Research was conducted in 2014 and 2015 to determine if two common commercial acetolactate synthase (ALS) inhibitor herbicide formulations, that contain the crop safener isoxadifen, could be used on field corn (Zea mays L.) hybrids with reported ALS sensitivity. Two ALS‐sensitive field corn hybrids (DEKALB DKC 62‐08 and DKC 64‐69) were treated 18 to 21 days after planting with nicosulfuron + rimsulfuron + isoxadifen or thiencarbazone + tembotrione + isoxadifen at 1× and 2× labeled rates. No interactions were observed between herbicide treatment and field corn hybrid. When averaged over herbicide treatment, DKC 62‐08 produced less aboveground biomass and was shorter in height than DKC 64‐69. However, no difference in grain yield between hybrids was observed. When averaged over corn hybrid, only the 2× rate of tembotrione + thiencarbazone methyl + isoxadifen caused a significant reduction (19%) in aboveground biomass. Nicosulfuron + rimsulfuron + isoxadifen and tembotrione + thiencarbazone + isoxadifen, at both 1× and 2× rates, reduced plant height up to 3 inches 26 days after treatment (DAT). However, only the 2× rates of these safened herbicides caused significant height reductions 62 DAT. Both herbicide formulations at 1× and 2× labeled rates caused corn yield losses of 11 to 16 bu/acre. These data suggest that these particular commercial herbicide formulations can cause crop injury and subsequent yield loss when used on ALS‐sensitive field corn hybrids.