Contact herbicidal activity optimization of methyl capped polyethylene glycol ester of pelargonic acid

Abstract

The loss of important contact herbicides like paraquat opens opportunities for more potentially sustainable solutions demanded by consumers and organizations. Frequently, for adequate weed control, the alternatives to classical synthetic products need well-defined and executed labels and even more detailed use descriptions. One novel candidate with rare contact activity is a pelargonic acid ester of methyl polyethylene glycol (PA-MPEG) with advantages over free pelargonic acid (PA), such as reduced volatility and ease of formulation. Here, we report on the role of the application parameters such as spray volume, rate, sprayer set-up, and climate conditions for weed control with PA-MPEG. At a dose rate of 12.8 kg ae ha−1 in a spray volume of 500 L ha−1, control of Digitaria sanguinalis (L.) Scop. and Solanum nigrum L. was excellent. These values for product rate and spray volume are lower than applications with commercial PA herbicides, at equal or better efficacy. Coverage was too low at spray volumes of 100 to 200 L ha−1, for adequate contact activity of both PA-MPEG and PA. Weed control was significantly increased when PA-MPEG application was made at lower boom height with reduced distance to weed canopy, or under warm and dry climate conditions. The results indicate the potential of PA-MPEG under optimal use conditions as a new contact herbicide in integrated weed management.