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Vegetable IPM Updates Archive
Cooperative Extension
Weed Control (May 5, 2010)

Prefar (Bensulide) is one of the very limited number of herbicides registered on small acreage vegetable crops and one of only two herbicides currently registered on leaf lettuce to control broadleaf and grass weeds. Although this herbicide was first registered 45 years ago, we are still learning how to use it most effectively. Prefar controls a relatively narrow spectrum of weeds which include annual grasses, pigweed, purslane, goosefoot and lambsquarters. Control can vary from 0 to 100% even on these sensitive weeds. Much of this variation is caused by irrigation method and amount. Prefar adheres very strongly to the soil surface and must be moved with water down to where the weed seeds are germinating. This is often within the top 0.5 inch of soil and can be accomplished by applying at least 0.5 inch of water through sprinklers. Less water than this can be ineffective. Furrow irrigation will not move Prefar into the soil. Light mechanical incorporation is sometimes recommended but will often dilute the herbicide too much and result in poor weed control. More information on this subject can be obtained in this paper.

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For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.

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