Broadleaf weed control in cotton continues to be a problem for Arkansas producers. The development of DPX-PE350 as a postemergence herbicide will provide producers with a tool they have never had, a safe over-the-top herbicide.

In 1989 we evaluated KIH-8921 (now DPX-PE350) applied preemergence and postemergence in cotton. The lowest rate tested was 1.2 oz ai/A. From the tests conducted in 1989 we observed better prickly sida (Sida spinosa) control with preemergence versus postemergence applications. Conversely, pitted morningglory (Ipomoea lacunosa) was best with postemergence compared to preemergence applications. In 1990 we evaluated DPX-PE350 applied preemergence at rates of 0.4 to 3.2 oz ai/A. Forty-one days after treatment prickly sida control was 88% and entireleaf morningglory (Ipomoea hederacea, var. integriuscula) control was 39% with the 0.4 oz ai/A rate. In 1991 tests were expanded to evaluate lower rates and more weed growth stages. DPX-PE350 applied preemergence at 0.125 oz ai/A provided 78% prickly sida and 8% entireleaf morningglory control 40 days after application. When DPX-PE350 was applied at 0.5 oz ai/A to 1 to 3 leaf entireleaf morningglory and 2 to 3 leaf prickly sida, control was 78 and 66% at 30 days after treatment, respectively. Applications to 7 to 9 leaf entireleaf morningglory and 4 to 6 leaf prickly sida at 0.5 oz ai/A gave 74 and 59% control at 26 days after treatment, respectively. Spotted spurge (Euphorbia maculata) was evaluated in one test, and like prickly sida was controlled better with preemergence and very early postemergence applications when compared to normal postemergence timing. DPX-PE350 at 0.25 oz ai/A applied preemergence gave 88% control at 37 days after application. Spotted spurge control was 77% when DPX-PE350 was applied very early postemergence at 0.5 oz ai/A. Application made 7 days later provided 0 and 14% control at 0.5 and 1.0 oz ai/A, respectively.

From these tests we concluded that prickly sida was controlled best with reduced rates applied preemergence or possibly very early postemergence. Morningglory control was best with reduced rates applied postemergence.