Peanut Cultivar Response to Diclosulam in the Southwest Peanut Growing Region

Field experiments were conducted in the south Texas and Texas High Plains area during the 2018 through 2020 growing seasons and in southwestern Oklahoma in 2020 to evaluate runner peanut cultivars (Georgia-13M, Georgia-09B) and the Spanish cultivar (Ole´) tolerance to diclosulam at 0.026 (the manufacture’s recommended use rate) and 0.052 (twice the manufacture’s recommended use rate) kg ai/ha applied preemergence (PRE) or peanut cracking (CRACK). No diclosulam injury was noted in south Texas; however, in the Texas High Plains and Oklahoma locations significant stunting was noted with diclosulam applied PRE especially under sprinkler irrigation. In 2018 at the High Plains location, under furrow irrigation, no peanut stunting was noted. In 2019 and 2020, under sprinkler irrigation, diclosulam at 0.026 and 0.052 kg/ha applied PRE resulted in early-season stunting of 18 to 59% in both Oklahoma and the Texas High Plains. No late-season stunting was noted in Oklahoma; however, up to 20% stunting was still visible at the Texas High Plains location. No yield differences were noted in south Texas or the High Plains region in 2018 or 2020; however, in 2019 at the High Plains location, peanut yield decreased as diclosulam rate increased but application timing had no effect. At the Oklahoma location, application timing and rate effect were noted. Diclosulam applied PRE and the high rate of diclosulam reduced peanut yield. Issues still exist with diclosulam in the southwest peanut growing areas as seen previously in 2000 despite the different varieties planted. There may be opportunities to utilize diclosulam postemergence (POST) since peanut injury was 5% or less and yields were not reduced when applied CRACK.