The effect of two prey species, Chrysomphalus aonidum and Corcyra cephalonica, on the quality of the predatory thrips, Aleurodothrips fasciapennis, reared in the laboratory

Periodic and augmentative releases of natural enemies are often required to enhance biological control and integrated pest management programs. One re quirement for these programs to be practical is that natural enemies can be easily and economically mass-reared. This study assessed the effects of di et on the quality of the F-3 and F-4 laboratory-reared generations of the p redatory thrips, Aleurodothrips fasciapennis. Diets were eggs and crawlers of the diaspidid scale Chrysomphalus aonidum and eggs of the pyralid moth C orcyra cephalonica. It was found that both the F-3 and F-4 generations were not viable when reared on the eggs and crawlers of C. aonidum due to very low fecundity and, in the F-4 generation, increased larval mortality. In co ntrast, thrips reared on the eggs of C. cephalonica were viable in both gen erations but an increase in larval mortality from the F-3 to the F-4 genera tion did result in a reduction in viability. These results are discussed in terms of genetic, environmental and behavioural factors that may have infl uenced the quality of the thrips. It is concluded that genetic factors (inb reeding suppression, genetic drift or selection), the behaviour of scale cr awlers and the predatory behaviour of thrips were probably of little value in explaining the results. The most likely explanation was that the diet su pplied to thrips was of inadequate nutritional quality. It was not possible to distinguish whether this was due to low intrinsic quality of the prey o r an indirect effect of experimental conditions on prey quality.