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Post-harvest is a good time to initiate weed management plans for annual, biennial, and perennial weeds. Achieving and maintaining post-harvest weed management can help decrease weed pressure, herbicide-resistant weed species, and costs associated with field preparation for the next growing season.
During and after harvest, scout fields to determine the weed species present and control these weeds until temperatures are low enough to limit germination. Any summer annual weeds that were cut-off during harvest need time to produce new leaf growth prior to a herbicide application. Weed management strategies can include:
Keep in mind that post-harvest tillage may move weed seed towards the soil surface and encourage germination. To prevent the spread of weed seed, clean tillage equipment before moving to a new field.
Fields with crops that are planted earlier in the season like corn, sorghum, and in certain locations, cotton, have an extended period of time to support the growth and production of weed seeds. It is important to control this potential weed seed production, especially for hard to control weeds like waterhemp and/or Palmer amaranth, common ragweed, and giant ragweed.
Pigweeds have the ability to flower when only a few inches in height, and can produce seed only two weeks after flowering. Weeds should be controlled by cultivation or herbicide application when they are less than two to three inches tall.5
Several herbicide options are available to help provide post-harvest weed management. A non-selective herbicide may be used after harvest to kill vegetation in the field. When glyphosate-resistant weeds like pigweed are present, use paraquat or a tank-mix of Roundup PowerMAX® Herbicide + 2,4-D or dicamba, depending on cotton trait planted for post emergent weed control and cotton stalk destruction. When using paraquat herbicides to manage tough to control weeds such as pigweed, apply prior to weeds reaching 3-inches in height for the most consistent control.
To broaden and lengthen weed management, a residual herbicide should be added to the tank. Refer to product labels for tank mix partners. Residual herbicide selection is critical since some products may remain active in the soil and may influence the selection of next year’s crop. Herbicide labels should be checked for plant back and rotational crop restrictions. Because of the array of herbicide products and strategies available, it is important to work with your local brand representative for the best options for your fields.
Keep in mind, following harvest, it is important to allow time for regrowth of weeds to occur before herbicide applications are made.
Fields with weeds that set seed in the fall may have dramatically higher weed populations during the next growing season. Knowledge of the weed species in a field and the competitiveness, emergence pattern, and density of the weed community can be used to develop effective herbicide programs. Other management practices can be developed to minimize reduction in yield potential, herbicide resistance, and control aggressive weed species. Controlling weed populations post-harvest can help reduce weed populations from year to year and allow for more efficient use of herbicides and cultural practices during the growing season.
It is important to remember that the main goal of the selected strategy is to prevent weed seed production. For tough to control weeds in your area, work with your local brand representative to identify the best weed management strategy to implement, and visit www.roundupreadyPLUS.com for the latest information and recommendations for weed management.