The impact of Palmer amaranth in Indiana
• Genetic Diversity: Dioecious reproduction in which individual plants are either male or females, which forces outcrossing and genetic diversity. This gives Palmer amaranth the ability to adapt and quickly spread herbicide-resistance genes when selection pressure is applied, such as repetitive use of single mode of action herbicides.
• Seed Production: Palmer amaranth is a prolific seed producer with plants producing at least 100,000 seeds in competition with a crop, and upwards of a half million seeds in non-competitive scenarios.
• Seed Size: Palmer amaranth seeds are rather small and thrive in no-till or minimum tillage fields where seeds are allowed to stay in the ideal emergence zone in the top inch of soil. The small seeds are easily transported by humans either through grain, seed, or feed contamination; and they are also transported on equipment such as combines.
• Aggressive and Competitive: Palmer exhibits aggressive growth and competitiveness with plants growing 2-3” per day in ideal conditions and creating yield losses of 11-91% in corn and 17-79% in soybean when allowed to compete throughout the growing season.
• Herbicide Resistance: Palmer populations have conferred resistance to multiple herbicide modes of action including: ALS inhibitors, triazines, HPPD-inhibitors, dinitroanilines, and glyphosate, with a large majority of southern populations being glyphosate- and ALS-inhibitor-resistant.