Cole Crops and The Dinitroaniline (yellow) Herbicides (November 27, 2013)

Two of the dinitoanaline herbicides, Pendimethalin (Prowl) and Trifluralin (Treflan), are registered for use on cole crops in Arizona. They are generally safe to use but must be properly incorporated or injury can occur.

These herbicides are used preemergence and work the same way to kill weeds. They stop cell division in in the roots and shoots of developing seedlings. They move very little in the plant and work only on the roots and shoots that contact them. Growth is stopped at the point of contact. The symptoms that can be seen are a lack of root development and swollen or brittle stems if much of the herbicide is concentrated at or near the soil surface.

Both of these herbicides are generally safe to cole crops if they are mixed into the soil prior to planting or transplanting the crop. Prowl incorporates adequately with overhead sprinkler water although Trifluralin must be mechanically incorporated. If too much herbicide is at the surface the stems of the crop can become brittle, swollen and break off.

We have established a laboratory at the Yuma Agriculture Center to help growers and Pest Control Advisers determine the levels of certain pesticides in their fields. Our focus has been upon herbicides in lettuce and other leafy vegetables but we have expanded our efforts and can now run several other products as well. We want to use this season to build a database and verify our procedures. We are running samples free of charge this season and our turnaround time is normally one day or less. We need one pound of soil or 20 grams (a small baggy) of plant material as a composite sample taken separately from affected (showing symptoms) and unaffected (no symptoms) areas across each field. Soil should be collected from the top 2 inches. Samples should be put in paper bags and labeled as “affected” or “not affected” with the location, crop, your name and phone number, date and the pesticides you want to check for. Please call either myself (928-580-9902) Marco Pena (928-782-5871) or Octavio Lopez (928-919-8736) to let us know you are bringing them or have questions.

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