Reducing Imazethapyr Injury to Field Corn (Zea mays) with Naphthalic Anhydride

Abstract

A field trial was conducted in 1988 and 1989 to confirm the efficacy of naphthalic anhydride (NA) for providing full-season protection of corn from imazethapyr applied at various times and rates. NA applied as a 1% by weight dust to corn seed caused 6% injury 2 weeks after treatment (WAT) in 1989; however, plants recovered within 6 WAT and grain yield was not affected. Imazethapyr applied to corn untreated with NA resulted in greater than 30% injury for all treatments in both years except PRE in 1988. NA reduced phytotoxicity from all imazethapyr applications in 1989 and from PPI, early POST, and 4- to 5-leaf stage (mid-POST) applications in 1988. Despite the safening effect, corn injury was still observed 6 WAT in NA-treated corn for all imazethapyr applications in both years except early POST in 1988. Higher yields were produced from NA-treated than untreated corn with imazethapyr applied PPI in both years, PRE in 1989, early POST in both years, and mid-POST in 1988. Safened corn treated PPI and early POST yielded the same as the safened corn in the control in both years. Imazethapyr applied at the 8- to 10-leaf stage caused total yield loss regardless of NA treatment. Drought conditions may have caused the lower corn injury and yield loss from imazethapyr observed in 1988 compared to 1989.

The Basis of Imazethapyr Tolerance in Cowpea (Vigna sinensis)

“…In greenhouse experiments, com shoot fresh weight was reduced 54% (15) and 50% (2) by 112 and 240 g ha-I foliar applied imazethapyr, respectively. Foliar applications of 140 or 280 g ha-I imazethapyr caused 43% or more injury to field grown com (4). In previous studies, greenhouse grown soybean was not injured until at least (80:20:0.25 by volume), rather than in an aqueous spray solution as we did.…”