Beet armyworms and cabbage loopers have been very active in desert crops over the past few weeks and are historically the most important pests of produce during September and October. Worm pressure has been light the past few fall growing seasons, but this year populations overall appear to be moderate to heavy throughout the area. Armyworms are especially abundant on produce crops, where at the Yuma Ag Center they are presently averaging more than 2 larvae per plant in untreated lettuce. Cabbage loopers were relatively light on fall melons this year, but are now beginning to show up fairly consistently , especially on cole crops. Remember, temperatures drive larval development and adult activity, particularly when night time temps remain high. Now that temperatures have dropped a bit, worm activity can be expected to slow down, but certainly won't disappear. If temps climb back up into the 90's in the next week or so, this could extend worm activity for several more weeks. Fortunately, there are a number of very effective insecticides that can be applied as stand-alone products that provide effective residual control of both of these lepidopterous species. Research trials have showed that these products provide comparable control on lettuce and cole crops during September and October. Before selecting a product for Lep control, be conscious of products (chemistries) previously used on the crop. Avoid using products with the same mode of action more than twice on any given field. Detailed information on the insecticides available for effective control of beet armyworm and cabbage looper can be found in these documents: Lepidopterous Larvae Management in Desert Produce Crops and Knockdown and Residual Control of Lepidopterous Larvae on Head Lettuce.

To contact John Palumbo go to: jpalumbo@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.