Management of Palmer amaranth in Illinois
If scouting reveals additional Palmer amaranth plants have emerged, make a second application of a foliar-applied herbicide before Palmer amaranth plants are four inches tall.
Species Biology: Palmer amaranth seed production
Palmer amaranth (like waterhemp) is a dioecious species, meaning plants are either male or female. Male plants produce pollen and female plants produce seed, which makes Palmer amaranth an obligate outcrossing species. Outcrossing species tend to have more genetic diversity then self-pollenated species and this can hasten the evolution of herbicide resistance. Transfer of herbicide-resistance traits via pollen can quickly spread these traits across the landscape. Research has demonstrated that female Palmer amaranth plants are capable of producing numbers of seed comparable to that of waterhemp (several hundred thousand to over one million).
Recommendations based on Palmer amaranth seed production:
1. Physically remove any remaining Palmer amaranth plants before the plants reach the reproductive growth stage. Plants should be severed at or below the soil surface and carried out of the field. Severed plants can root at the stem if left on the soil surface, and plants can regenerate from stems severed above the soil surface.
This publication was made possible through funding by the United Soybean Board and collaboration among several university and private industry partners.
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