Palmer amaranth (Amaranthus palmeri) has invaded the fields of North Dakota. Recognized as one of the most yield-robbing weeds in agriculture, the North Dakota Department of Agriculture wasted little time adding Palmer amaranth to the noxious weed list. Concern over its devastating effects has made the weed a popular topic at ND expos and conferences. One common theme during these discussions was to inform growers on how to differentiate Palmer amaranth from other ND pigweeds, specifically Waterhemp (A. tuberculatus) (Ikley and Jenks, 2019). The window of opportunity for effective herbicide treatments is limited to shortly after emergence, and before the weeds reach 3 inches. This early detection in the field can mean the difference between shutting down an early infestation and a permanent increase in annual herbicide to curtail an established population of this highly productive weed (Parnell et al., 2017).

Unfortunately, visual identification at the vulnerable and early stage are challenging for even the most experienced weed scientists. Moreover, nature is not always textbook, making it difficult to fully document the overwhelming variation among individual Palmer amaranth plants, which can arise from field or regional differences in soil types, nutrient loads, and water availability (Legleiter and Johnson, 2013). As a result, photographs that are used to help growers differentiate amaranth species can fall short, potentially causing further confusion and inadequate control recommendations. Thus, the most reliable way to confirm Palmer amaranth and other pigweed species is to supplement the visual diagnosis with a DNA test. Since identification is difficult and effective control is time-dependent, the National Agricultural Genotyping Center (NAGC) partnered with weed scientists at North Dakota State University to make a rapid DNA test available to the agricultural community.

This project was funding by the National Corn Growers Association, North Dakota Soybean Council, and the North Dakota Corn Council.

References

Ikley, J. & Jenks, B. 2019. Identification, Biology and Control of Palmer Amaranth and Waterhemp in North Dakota [Online]. North Dakota State University. Available: https://www.ag.ndsu.edu/publications/crops/identification-biology-and-control-of-palmer-amaranth-and-waterhemp-in-north-dakota.

Legleiter, T. & Johnson, B. 2013. Palmer Amaranth Biology,  Identification, and Management [Online]. Purdue University. Available: www.extension.purdue.edu/extmedia/ws/ws-51-w.pdf.

Parnell, S., Bosch, F., Gottwald, T. & Gilligan, C. 2017. Surveillance to Inform Control of Emerging Plant Diseases: An Epidemiological Perspective. Annual review of phytopathology, 55.