Management of Glyphosate-Resistant Waterhemp in Corn and Soybean (2008)

Abstract

Waterhemp, Amaranthus rudis, is a summer annual weed in the pigweed family that is found throughout the Midwest. Waterhemp seedlings have oar-shaped or oval cotyledons (seed leaves) and are hairless unlike redroot or smooth pigweed. Mature waterhemp plants have long, lance-shaped leaves that are waxy or glossy in appearance. Plants can range in height from 4 inches to 12 feet depending on growing conditions, and they can grow as much as 1 inch per day during the summer growing season. In surveys conducted in Illinois and Missouri, producers and agricultural retailers listed waterhemp as one of the most common and troublesome weeds encountered in soybean production.