Grasp (penoxsulam or DE-638) is a new herbicide from Dow AgroScience that should have a federal label prior to the 2005 growing season. Grasp was evaluated for control of alligatorweed in producer fields near Eagle Lake, TX for two years. In the studies herbicide treatments were made at two timings; early postemergence (EPOST) at the three leaf rice stage with alligatorweed 3 to 5 inches tall, and late postemergence (LPOST) at the five leaf rice stage and alligatorweed 6 to 8 inches tall.

Grasp was applied at 0.027 lb ai/A alone and in combination with Stam at 2.0 lb/A and Grandstand at 0.187 lb/A EPOST; and with Stam at 4.0 lb/A and Grandstand at 0.187 lb/A LPOST. A tankmix of Stam/Grandstand without Grasp was also evaluated at each application time. Grasp alone provided greater than 80% alligatorweed control for both timings. Addition of Grandstand to DE-638 improved alligatorweed control to better than 93%. A tankmix of Grasp with Stam provided less than 50% control indicating some antagonisms. A tankmix of Stam/Grandstand without Grasp provided less than 20% control. Optimum alligatorweed control was observed with Grasp under moist soil conditions with control decreasing under dry soil conditions.

Research on these projects were conducted by John O’Barr, Garry McCauley and Mike Chandler. For more information contact Dr. Mike Chandler at 979-845-8736 or email jm-chandler@tamu.edu.