Common pokeweed is a competitive, simple perennial broadleaf weed that produces abundant seed, making it a frequent problem in agronomic crops in Pennsylvania. Traditionally, tillage was used to manage pokeweed; however, the wide-spread adoption of no-till, as well as a decline in the use of diverse crop rotations and soil-residual herbicides, may have allowed pokeweed populations to increase in recent years. The objective of this research was to identify effective herbicides for control of common pokeweed in corn and soybean. Herbicide efficacy experiments were conducted in separate locations from 2011 to 2013 to determine the effectiveness of POST corn and soybean herbicides for control of pokeweed. Glyphosate-resistant corn and soybean varieties were used and several herbicides were evaluated alone and in combination. The results from this work show that glyphosate is an important herbicide for successful control of pokeweed in soybean. When glyphosate was included, 79 to 91% control was achieved, while for treatments not containing glyphosate, control was not greater than 62%. In corn, several non-glyphosate herbicides, including 2,4-D, dicamba, and mesotrione plus atrazine, are options in addition to glyphosate for controlling pokeweed. Most corn treatments provided at least 80% control throughout the season and significantly reduced common pokeweed biomass compared to the nontreated control. In the year after application, pokeweed control was found to be similar to the results from the previous fall in both corn and soybean.
Nomenclature: Atrazine; dicamba; mesotrione; glyphosate; 2,4-D; common pokeweed, Phytolacca americana L. PHTAM; corn, Zea mays L.; soybean, Glycine max (L.) Merr.