The influence of host deprivation and egg expenditure on the rate of dispersal of a parasitoid following field release

The results suggest that to enhance local establishment in a fragmented environment parasitoids should be given access to hosts prior to release, and host deprivation could be used to encourage broader dispersal if large numbers can be released at each release site to counteract the dilution effect of dispersal.

Abstract

With a view of improving the establishment of Mastrus ridibundus, a potential candidate for the biological control of the codling moth in California, a series of studies were undertaken to investigate the effect of a pre-release treatment with or without hosts on different performance characteristics. The post-release dispersal of M. ridibundus females was investigated in this study, using mark-release-recapture experiments with immunological markers. The results suggest that, in general, M. ridibundus is high dispersive. In the absence of any host stimuli for at least 4 days before release, females showed a strong dispersal response with an average dispersal rate of 81.50 m2/h. In contrast, females continuously provided with hosts before release or deprived of hosts for only a short period of time (1–2 days), showed a lower rate of dispersal averaging 2.07 m2/h. These results suggest that to enhance local establishment in a fragmented environment parasitoids should be given access to hosts prior to release. In contrast, for regional establishment in a less fragmented environment, host deprivation could be used to encourage broader dispersal if large numbers can be released at each release site to counteract the dilution effect of dispersal.