Tall waterhemp is one of the most problematic weed species throughout the Midwest and has now arrived and spread to eight counties in Upstate New York (Figure 1).

It also happens to be one of our weed species that is glyphosate-resistant or better known as Roundup-resistant. Recent research conducted by Dr. Bryan Brown, Integrated Weed Management Specialist at the Geneva Experiment Station, has found 2 populations of waterhemp that survived an application of atrazine, imazethapyr (Pursuit) and glyphosate - meaning these populations are resistant to multiple Modes of Action (MOA's). Waterhemp is a part of the pigweed family and has evolved resistance to herbicides very quickly. Waterhemp is dioecous, meaning there are separate male and female plants. Another reason this weed is problematic is that it grows very rapidly and can produce more than 1 million seeds per plant. It competes for sunlight, water and nutrients. Waterhemp can spread from field-to-field and farm-to-farm on equipment, clothing, application equipment, or via water from over flooded ditches and rivers. Currently, research is being conducted to evaluate various PRE and POSTEMERGE herbicide options for controlling this weed in both corn and soybeans here in New York. It is important to know the difference between this weed and other pigweed's like it.