Wheat is commonly grown following lettuce that was treated with soil active herbicides. The most commonly used lettuce herbicides are Balan(benefin), Kerb(pronamide) and Prefar(bensulide). All 3 of these are root and shoot growth inhibitors that effect grasses and slight and temporary injury to wheat is not uncommon. Yield lose is rare. Wheat is a fairly large seeded grass that is vigorous enough to overcome some injury. Two herbicides, trifluralin (Treflan) and pendimethalin(Prowl) that have this same mode of action are registered for use on wheat in some states. Where trifluralin is used, the wheat is normally planted below the treated soil. Pendimethalin is used here on wheat after it is established and has a good root system. All of the lettuce herbicides are normally put on during crop establishment and have had at least 3 or 4 months to dissipate. Persistence of Balan, Kerb and Prefar is variable but is normally 2 to 6 months. When these herbicides are applied in a band, it is often possible to see some stunting in this band at the early stages of the wheat crop. Wheat will normally outgrow this.

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To contact Barry Tickes go to: btickes@ag.arizona.edu.

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.