Investigation of the Influence of Low Drift Nozzles and Weed Density on Herbicide Deposition and Efficacy.

The introduction of Roudnup 2 Xtend soybean (resistant to dicamba and glyphosate) and the registered formulations of dicamba (Xtendimax, Engenia, and FeXapan) placed a new tool in the hands of farmers to control troublesome broadleaf weeds. Although the introduction of these technologies did not come without issues as millions of acres of sensitive soybean were injured from offsite movement of dicamba from Xtend fields. Tight restrictions have been placed on the dicamba labels in an effort to mitigate the movement of dicamba, including restrictions of applications with specific nozzles that produce extremely coarse and ultra coarse droplets. Applications with droplets in the ultra coarse and very coarse droplet range can lead to reduced herbicide deposition, especially under non ideal conditions. The use of drift reduction agents (DRA) that are often required with tank mix partners such as Roundup PowerMax may also further influence deposition. The focus of this research project is to understand how weed density, specifically with waterhemp and Palmer, influence herbicide deposition and efficacy when using a low drift nozzle and DRA. A second objective of the project will be understanding the influence of low drift nozzles and DRA’s on the deposition of herbicides on Poacea (grass) species. The results of this research will be used to educate farmers and pesticide applicators on the best parameters for making dicamba plus glyphosate applications that reduce the risk of drift while maximizing deposition of the herbicide solution onto target plants.