Effect of Glyphosate and Dicamba Drift Timing and Rates in Bell Pepper and Yellow Squash

Abstract

As dicamba resistance traits become more common in agronomic crops, the potential for off-site movement also increases. Little is known of how common vegetable crops will respond to dicamba drift. The objective of this study was to evaluate the effect of dicamba and glyphosate drift on bell pepper and squash growth as a function of application timing. The treatments were arranged in a factorial design with two timings by three rates and a nontreated check. The two timings were early bloom and midbloom (during bloom when fruit were present). The three rates were glyphosate at 21 + dicamba at 14 g ha−1, glyphosate at 10 + dicamba at 7 g ha−1, and glyphosate at 7 + dicamba 5 at g ha−1. Herbicides were applied with a controlled droplet applicator calibrated to deliver 2.34 L ha−1. In squash, crop injury was 26 to 31% at 3 DAT and 48 to 65% at 17 DAT. However, no differences were measured among application timings or rates for fruit weight or number at individual harvest or season total. Bell pepper injury ranged between 0 and 8% from 3 to 17 DAT and was not significantly different than the nontreated. However, large, Fancy, marketable, and total bell pepper fruit number were greater in the nontreated than glyphosate at 21 + dicamba 14 at g ha−1and glyphosate at 10 + dicamba at 7 g ha−1both years. The three rates of dicamba + glyphosate had a greater number and weight of cull fruit compared to the number of fruit in the nontreated plots. The cull fruit were shorter with a flattened appearance. Leaving bell pepper fruit on the plants longer may result in small and medium fruit becoming large or Fancy grade bell pepper fruit.