Considerations for Control of Palmer Amaranth and Other Pigweeds in Vegetables

Considerations for Control of Palmer amaranth and Other Pigweeds in Vegetables 

By Kurt Vollmer, Ph.D. Extension Weed Management Specialist

Palmer amaranth and other pigweeds have emerged and are thriving in some places. These weeds can quickly become too large and dense to control with many herbicides, so fields should be scouted and control measures implemented without delay. Shielded applications of herbicides, such as Gramoxone and Rely, applied at a spray volume of 20 gal/A can be used to control small smaller plants between rows. Most soil-applied herbicides labeled for vegetable production will only provide fair to good pigweed control. Consult the product label before using any herbicide, and be aware of any rotational restrictions before making an application.

Cultivation can be effective on small seedlings (<3 inches), but larger plants are likely to re-grow if roots or stem remain in contact with the soil. Since Palmer amaranth can emerge throughout the growing season, repeated cultivation is necessary for control. Adding straw or another type of mulch (980 to 1,960 lb./A) can help reduce the density of Palmer amaranth and other weeds. Larger Palmer amaranth and waterhemp plants should be pulled and disposed of properly. Plants should be bagged and buried or burned along the field’s edge. If working in a plasticulture system, plants will desiccate when placed on top of black plastic.

Regardless of the control method used, be sure to scout in a timely manner after each operation to determine if additional control is needed.

This article is featured in the Vegetable and Fruit News, Vol. 16, Issue 3.

Vegetable & Fruit News is a research-based publication for the commercial vegetable and fruit industry available electronically from April through October.  Published by the University of Maryland Extension Agriculture and Food Systems team.

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