THE USEFULNESS OF DESTRUCTIVE HOST FEEDING PARASITOIDS IN CLASSICAL BIOLOGICAL-CONTROL - THEORY AND OBSERVATION CONFLICT

1. We examine the conventional wisdom among biological control practit ioners that destructive host feeding is a desirable attribute in paras itoids employed for classical biological control, using both the predi ctions of population dynamics theory and historical data on biological control introductions of Hymenoptera against Homoptera. 2. Population dynamics theory predicts that destructive host feeders, compared with other parasitoids, are (a) either just as likely or more likely to be come established, and (b) unable to depress host equilibria as strongl y. 3. Analyses of the BIOCAT database suggest that among parasitoids o f Homoptera destructive host feeders are superior to other parasitoids with respect to both establishment rate and success rate. 4. We prese nt likely explanations for the disparity between the predictions of po pulation dynamics theory and the results of database analysis. A parti al explanation for the mismatch between theory and observation with re spect to the degree of pest suppression may be that females of destruc tive host feeding parasitoids rely less upon hosts as a food source wh en alternative foods such as honeydew and nectar are plentiful. 5. We conclude that, despite the predictions of population dynamics theory, destructive host feeders are probably better biological control agents than other parasitoids, and certainly no worse, but that it would imp rudent to use destructive host feeding as the sole, or even primary, s election criterion when seeking agents for classical biological contro l.