POTENTIAL FOR AUGMENTATIVE BIOLOGICAL-CONTROL OF BLACK BEAN APHID IN CALIFORNIA SUGAR-BEET

In northern California, black bean aphid (Aphis fabae Scopoli complex) can be a major pest of sugarbeet, particularly in spring-planted fiel ds. The major natural enemies of the aphid are predators, including th e coccinellids Hippodamia: convergens Guerin, Coccinella novemnotata H erbst & C. septempunctata L., and the chrysopids Chrysopa oculata Say & C. nigricornis Burmeister. Augmentative releases of eggs of either C hrysoperla carnea (Stephens) or C. rufilabris (Burmeister) failed to s ignificantly reduce aphid populations under field conditions. This was attributed in part to incompatibility between black bean aphids and l acewing larvae from commercial sources. Application of food sprays con taining yeast hydrolysate, sucrose and molasses resulted in increased densities of eggs and adults of C. carnea in treated plots. These resu lts suggest that the potential for augmentative biological control of black bean aphid through the application of food sprays is greater tha n that for release of commercially available lacewings. Regardless of method, an holistic approach to augmentation that takes into account t he ecological structure of the target agroecosystem will be required. Some aspects of ''pre-emptive'' biological control are discussed.