Pre and Post Herbicides in Combination with a Rye Cover Crop for Control of Yellow Nutsedge and Pigweed in Watermelon

Abstract

Production of watermelon (Citrullus lanatus L.) is a highly profitable crop in the Southeastern United States; however, adequate weed management is lacking due to the limited number of registered herbicides. Field studies were conducted in the summer of 2011 and 2012 in Auburn, Alabama, to evaluate the efficacy of selected preemergence (pre) and postemergence (post) herbicides in combination with a winter rye cover crop for controlling yellow nutsedge and smooth and redroot pigweed. Herbicide treatments included all combinations of two levels of ethalfluralin applied pre (none and 1900 g·ha−1) along with 4 levels of post-applied herbicides. The four post herbicides included halosulfuron (54 g·ha−1), glufosinate (340 g·ha−1), carfentrazone (35 g·ha−1), and none. The treatment consisting of no pre or post herbicides is referenced as cover crop only (CCO). Pigweed density was reduced by all herbicide treatments in comparison to the CCO treatment. Ethalfluralin applied pre followed by glufosinate post provided the greatest control of pigweed and was similar to ethalfluralin pre followed by either halosulfuron or carfentrazone post as well as glufosinate post (no pre). In comparison to the CCO treatment, yellow nutsedge density was significantly reduced by both treatments containing halosulfuron (ethalfluralin pre plus halosulfuron post; halosulfuron post) in addition to plots treated with glufosinate post. Watermelon yield and subsequent crop value was highest in plots receiving ethalfluralin pre followed by glufosinate post and was similar to the treatment of ethalfluralin pre followed by carfentrazone post. Use of pre- and post-applied herbicides along with a rye cover crop could improve control of pigweed species and yellow nutsedge and led to an increase in watermelon yield and subsequent crop value.