The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz., released Nov. 16, 2011.

Aphid identification in leafy vegetables

By John Palumbo, UA Research Scientist and Extension Specialist

The proper identification of winged-aphid species found on leafy vegetables in the desert is important for cost-effective pest management. This is the time of the growing season when we often observe winged (alate) aphids in desert lettuce and cole crops.

Most of the important aphid species found on local crops do not over summer here because of high temperatures. They typically begin migrating onto desert crops beginning in November; often blown in with gusting winds.

My experience over the past 20 years suggests this is due in part to cooler weather and changes in prevailing winds that now begin to blow into the area from the north and northwest.

Once the aphids reach the desert valleys, they typically move from crop to crop until they find a suitable host to feed and colonize. It is not uncommon to find winged aphids on lettuce or broccoli that are specific pests of small grains (i.e., corn leaf aphid) or alfalfa (i.e., pea aphid).

Since these aphid species will not colonize lettuce, it is important to distinguish them from the key aphid pests commonly found on lettuce that colonize and require management to prevent problems at harvest (green peach aphid, foxglove aphid, lettuce aphid). Also, you are likely to find cowpea aphid in lettuce as it is common in alfalfa at this time.

Experience has shown that although small colonies may be found on lettuce the populations rarely increase in lettuce crops.

The bottom line is proper aphid identification can save pest control advisers (PCAs) time and money and prevent unnecessary insecticide applications.

A simple pictorial key provides information to assist PCAs with identifying winged aphids important in lettuce and other leafy vegetables. Click on the following link to view the Aphid ID tool.

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