Comparison Between Diclosulam- and Imazapic-Based Weed Control Systems in Peanut1

Field studies were conducted in Florida and Alabama in 1998 and 1999 to evaluate imazapic [70gai/ha preemergence (PRE) or early postemergence (EPOST)], diclosulam (18 or 26 g ai/ha PRE or 18 g/ha EPOST) or imazapic + diclosulam (35 + 13 g/ha PRE or 35 + 9 g/ha EPOST). These treatments were applied alone or supplemented with either a paraquat + bentazon tank mixture or 2,4-DB. The intent was to determine if diclosulam, which has a mode of action similar to imazapic and is less persistent and less costly, could be incorporated into systems with other herbicides and thereby offer an alternative to imazapic. Maximum yield and economic return were consistently associated with only two treatments, imazapic at 70 g/ha EPOST and imazapic + diclosulam at 35 + 9 g/ha EPOST. However, none of the diclosulam-based systems provided a more favorable economic return than imazapic applied alone due to poor sicklepod control with diclosulam. Sicklepod control with diclosulam was improved with the addition of either paraquat + bentazon or 2,4-DB, but control was less than that obtained with imazapic. Diclosulam-based systems could be identified that were as effective as imazapic alone in controlling Florida beggarweed (diclosulam 26 g/ha EPOST or imazapic + diclosulam PRE or EPOST), bristly starbur (diclosulam 18 g/ha PRE or imazapic + diclosulam PRE or EPOST) and yellow nutsedge (imazapic + diclosulam EPOST). Thus, diclosulam-based systems may offer an economic advantage over imazapic in areas void of sicklepod. Neither diclosulam nor imazapic adversely affected any of five runner-type peanut cultivars (Georgia Green, Southern Runner, ViruGuard, Florida MDR 98, or Florida C-99R) when applied at twice labeled rates.