In-Field Insectaries for Vegetable Crops

Bill Chaney
UCCE Monterey Cnty, 1432 Abbott St, Salinas CA 93901

Aphids are the major pest of many vegetables in the coastal areas of California. Attempts to control aphids without conventional insecticides have not been successful in most large-scale commercial applications. Recently, leafminers have become an increasing problem in these crops as well. This study used a multi-disciplinary approach to evaluate the feasibility of using areas of growers' fields devoted to non-crop plants as insectaries. In these areas beneficial insects and other beneficial arthropods could find food and shelter. It is hoped that by providing such areas, the populations of beneficial organisms could be increased to such a level that pest populations would be reduced on adjoining crop plants. It is known that many beneficial organisms such as parasitic wasps, green lacewings, syrphid flies, etc., need nectar and pollen as adults while feeding on aphids as immatures.

The first year of the project looked at many potential plants that might serve such a purpose, including some of the cover crops that are being grown in the area. The plants must grow quickly and be attractive to the beneficials without harboring too many pest insects or diseases. Lettuce was chosen as the first test crop since its major pest, the green peach aphid, is a good target for control by beneficials. It presents a challenge in being a short season crop, requiring as little as 60 days for development in some situations.

The in-field portion of this work was done on both conventional and organic growers' farms. The goals were to examine the impact of these plantings on the number of beneficial insects and aphids in lettuce, to address the question of how far this impact might reach, and to determine if the beneficial insects will be able to effectively control the aphids to an acceptable level. Later a similar study was conducted in celery, looking at the impact of these insectaries on leafminer control.

Sweet alyssum was used in the field trials because of the consistently high number of beneficial insects it attracted and its fast growth and blooming, ease of establishment and lack of insects and diseases that might spread to lettuce. The level of control afforded by this technique was not acceptable to the growers when the in-field insectaries were used alone. Combinations and use of these insectaries as part of a total management system remains largely unexplored. There are also a number of other species of plants which should be explored for this and other cropping systems. The results to date do not support promoting this technique to growers of lettuce or celery in the Salinas Valley.

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