Herbicide Resistant Marestail (horseweed) in Pennsylvania
Marestail (also called horseweed) is one of the most challenging herbicide resistant weeds we face in Pennsylvania row crops. While some marestail in the state is not herbicide resistant, we hear a growing number of cases of glyphosate-resistant and ALS-resistant populations of this weed. Resistant marestail is especially challenging to manage after soybean planting, because effective herbicide options are extremely limited. Additionally, applications must be applied before the plants reach 4 inches tall for effective control. Therefore, optimal management of marestail in all row crops requires a proactive integrated approach. This video is Part 1 of a 2-Part video on marestail management. Part 1 covers important facts about marestail biology that growers should understand in order to best manage it. Part 2 covers the best management practices for marestail. We recommend watching both videos, starting with Part 1.