Potential for augmentative biological control of black bean aphid in California sugarbeet

In northern California, black bean aphid (Aphis fabae Scopoli complex) can be a major pest of sugarbeet, particularly in spring-planted fields. The major natural enemies of the aphid are predators, including the coccinellidsHippodamia convergens Guerin,Coccinella novemnotata Herbst &C. septempunctata L., and the chrysopidsChrysopa oculata Say &C. nigricornis Burmeister. Augmentative releases of eggs of eitherChrysoperla carnea (Stephens) orC. rufilabris (Burmeister) failed to significantly reduce aphid populations under field conditions. This was attributed in part to incompatibility between black bean aphids and lacewing larvae from commercial sources. Application of food sprays containing yeast hydrolysate, sucrose and molasses resulted in increased densities of eggs and adults ofC. carnea in treated plots. These results suggest that the potential for augmentative biological control of black bean aphid through the application of food sprays is greater than that for release of commercially available lacewings. Regardless of method, an holistic approach to augmentation that takes into account the ecological structure of the target agroecosystem will be required. Some aspects of “pre-emptive” biological control are discussed.