Monday, December 10, 2007 - 8:53 AM

Efficacy and release rate testing for Psyllobora vigintimaculata (Coleoptera: Coccinellidae), a potential greenhouse agent for biological control of powdery mildew

Andrew Sutherland,, University of California, Department of Entomology, One Shields Ave, Davis, CA

Powdery mildews are important plant pathogens worldwide, often warranting chemical control measures. Effects on non-target organisms and resistance concerns have recently prompted the consideration of biological control. A cosmopolitan coccinellid tribe (Psylloborini) is composed of obligate consumers of powdery mildew. A western North American species, Psyllobora vigintimaculata, is being evaluated for its ability to consume spores and hyphae of mildews in greenhouses, in an attempt at augmentative biological control. A predictive exponential consumption model has been created utilizing known biological attributes of the insect, a modified Leslie matrix, a previous individual larval consumption model and data from a feeding efficacy trial conducted in the greenhouse. The model has then been employed to simulate the population growth and subsequent removal of visible mildew colonies by the insects in a controlled horticultural system. When compared against real data from the efficacy trial, the model underestimates consumption, especially in the early time-periods. The modelís limitations and assumptions are discussed, as well as the possibility of using such a model as a calculator to determine the insect release-rate necessary to bring about control in a system with known parameters.

Species 1: Coleoptera Coccinellidae Psyllobora vigintimaculata
Species 2: Erysiphales various (powdery mildew)