HPC MSU

Publication Abstract

Evaluating the Effectiveness and Potential Interactions of Combining Triclopyr and 2,4-D for Eurasian Watermilfoil Control

Madsen, J. D., & Wersal, R. M. (2012). Evaluating the Effectiveness and Potential Interactions of Combining Triclopyr and 2,4-D for Eurasian Watermilfoil Control. Northeast Aquatic Plant Management Society Annual Meeting. New Castle, NH, January 17-19 2012.

Abstract

Invasive aquatic plant species are a widespread problem in the northeast, often occurring in aquatic habitats that in the past have proved difficult for management. Applying combinations of herbicides at permissible concentrations is one approach in which adequate concentrations and exposure times may be achieved. We tested combinations of liquid triclopyr and 2,4-D alone and in combinations ranging from 0.02 to 0.16 mg/L of triclopyr and 2,4-D from 0.08 to 0.64 mg/L. Statistically significant control with triclopyr required 0.08 mg/L, with only 68% control achieved with 0.16 mg/L of triclopyr alone. Statistically significant control with 2,4-D occurred at a threshold of 0.16 mg/L with 98% control at 0.64 mg/L. Combinations of 0.02 mg/L triclopyr and 0.08 mg/L of 2,4-D provided statistically significant control, with 90% control at four WAT with only 0.04 mg/L of triclopyr combined with 0.16 mg/L of 2,4-D. An analysis using the Colby equation indicated that the effectiveness of 2,4-D and triclopyr together is additive. Effective control with combinations of the two active ingredients at low concentrations enhances the potential for selective control and effective applications at low levels, where in-water concentrations may be limited by formulation and label restrictions.