The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz., released Oct. 5, 2011.

Beet armyworm and cabbage loopers in fall produce

By John Palumbo, UA Research Scientist and Extension Specialist

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. At the Yuma Agricultural Center, armyworms are averaging more than two 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, worm activity can be expected to slow down, but certainly will not disappear. If temperatures climb back into the 90s in the next week or so, this could extend worm activity for several more weeks.

Fortunately, there are very effective insecticides that can be applied as stand-alone products to provide effective residual control of these lepidopterous species. Research trials have shown that the 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.

Contact Palumbo: (928) 782-3836 or jpalumbo@ag.arizona.edu.