Palmer amaranth (Amaranthus palmeri) is a serious problem for many growers throughout the United States because of its competitiveness and effect on agricultural production.

Palmer amaranth is commonly confused with other pigweeds and is often difficult to identify in the early stages of growth. Much of the Palmer amaranth in the United States is resistant to several classes of herbicides such as glyphosate, and it’s common for many of these to be resistant to ALS-inhibiting herbicides such as Pursuit and Classic.

Last week, it was noticed in two dry bean production fields in Steuben County. This is the second population of Palmer amaranth to be found in New York, but is the first population to be found in a crop production setting. The fields are located along a high traffic roadway where it’s possible that the specimens came in on a tractor trailer or piece of machinery. It is important to know the biology of Palmer amaranth to avoid its potential to spread to surrounding counties.

Palmer amaranth is aggressive as it competes for nutrients, sunlight, and water. Palmer amaranth has dioecous reproduction, so individual plants are either male or female, which forces outcrossing and genetic diversity. Under ideal conditions, Palmer amaranth can grow 2-3 inches per day and within a few months of emergence, can reach heights of 6-8 feet. It is a highly prolific seed producer in that it can produce 100,000-600,000 seeds per female plant. The seed is also very small and can be transported via machinery, mud, or travel on the bottom of your shoe. As the plant matures, it forms a poinsettia appearance and is a key characteristic for identification.

It has been found that the presence of this weed species can double or triple your cost of management on the farm. If you suspect you have Palmer amaranth, contact your local field crop specialist or Cornell Cooperative Extension office to confirm identification and management strategy.

Josh Putman is a Field Crop Specialist SWNY Dairy, Livestock, and Field Crops Team