Beet armyworms and cabbage loopers have been very active in desert crops over the past week or so 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’s populations overall appears to be above normal. Armyworms have been heavy on produce crops for a couple of weeks. At the Yuma Ag Center they are presently averaging more than 1 larvae per plant in untreated lettuce. Similarly, cabbage loopers were fairly abundant on our fall melons this year, and egg lays and small larvae are beginning to show up on all produce crops in fairly large numbers. Remember, temperatures drive larval development and adult activity, particularly when night time temps remain high (in the mid-70s or higher). The higher temperatures we’ve been experiencing the past week or so is ideal for worm development and moth activity. As long as the average temperature remains around 85°F, worms should be active at damaging levels. Fortunately, there are a number of very effective insecticides that can be applied as stand-alone foliar products that provide effective residual control of both of these lepidopterous species. Radiant, Proclaim, Intrepid, Avaunt and any one of the Diamide products (Coragen, Belt, Voliam Xpress and Vetica) can provide good knockdown and extended residual control of armyworms and loopers. Research trials have showed that these products provide comparable control on lettuce and cole crops during September and October. Of course, residual control will often depend on the rate applied. In general, the higher the rate, the longer the residual, but this will also depend on how fast the plant is growing and plant size. 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. More information on the insecticides available for effective control of beet armyworm and cabbage looper can be found in this document: Lepidopterous Larvae Management in Desert Produce Crops.

Remember: When in Doubt-Scout.

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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.