Injury to lettuce from the three preemergence herbicides that are used; Benefin, Pronamide and Bensulide, occasionally occurs every year. Too little of these herbicides will not be effective and too much will cause crop injury. The injury symptoms that occur are similar to the symptoms caused by many other factors. The most accurate and precise method to diagnose pesticide injury is by laboratory analysis. Technology is available to detect very small amounts of pesticides in soil, plant tissue and water. Tenths of a part per million can routinely be detected of most pesticides. Without a local commercial laboratory that does pesticide analysis, it has been necessary to send samples out of state. This can take from a few days to a couple weeks. This is often longer than is optimal to make timely management decisions. There has been a need for a laboratory that can process pesticide samples locally in a day or two.

The Yuma Agriculture Center is a state of art facility and contains much of the same equipment used by commercial laboratories to process pesticide samples. The Arizona Iceberg Lettuce Research Council and The Specialty Crop Block Grant Program have granted us funds to develop the ability to process pesticide samples in a timely manner at The Yuma Agriculture Center. This lab is not intended to compete with commercial laboratories but is instead intended to help us work with the local industry to help diagnose pesticide injury in a timely manner and to help determine how to use pesticides most effectively. We have concentrated upon the most commonly used herbicides in lettuce this summer. These are Pronamide (Kerb), Benefin (Balan) and Bensulide (Prefar) but we expect to expand our capability to run other insecticides, fungicides and herbicides.

We hope to use this season as a time to gain experience using the equipment (a liquid chromatograph) and build a data base to help interpret the results. We will process samples free of charge and go over the results with you although this will be a learning season for us. We are currently prepared to run Kerb, Balan and Prefar and have found that the soil is a better indicator of the levels present of these three soil applied herbicides than is the plant tissue. We will need a total of approximately one pound of soil collected from the top inch in at least 20 random locations across the affected area of the field. Use paper bags rather than plastic and put them in the cooler labeled “samples” at the Yuma Valley Agriculture Center. It is behind the counter to the left when you come in the front door. Label the bag(s) with your name, phone number, the location it was collected and the pesticide(s) you need to measure. Please call either myself (580-9902), Octavio Lopez (782-5883, lab) or Marco Pena (782-5871) to let us know you will be bringing samples in.

Click picture to listen to Barry

To contact Barry Tickes go 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.