Biology and ecology of the predatory mite Iphiseius degenerans (Berlese)(Acari: Phytoseiidae)

Iphiseius degenerans (Berlese) is a predatory mite belonging to the family Phytoseiidae. Phytoseiid mites are economically important predators of phytophagous mites and insects in greenhouse crops. Mass reared phytoseiid mites are commercially available and used, amongst others, against spider mite and thrips infestations in greenhouse crops. Iphiseius degenerans is used commercially in Belgium for thrips control in greenhouse crops since 1994. A survey of the literature revealed that information on I. degenerans is relatively scarce. For instance, no records were found on life table parameters and functional responses when the predator was fed the western flower thrips Frankliniella occidentalis (Pergande). Also, there was no information found on the prey preference of the predatory mite. Nevertheless, these biological parameters are, among others, essential criteria for preintroductory evaluation of natural enemies for biological control in greenhouses. It can be concluded that, although I. degenerans has been used for years as a biological control agent, it is not clear how it interacts with its primary target, F. occidentalis. Laboratory studies were undertaken to elucidate interactions of I. degenerans with prey species the predator is likely to encounter in the crop. In the first experimental part of the study, population growth of I. degenerans was explored in relation to different food sources. The experiments conducted in this part revealed that the predatory mite is not able to complete development when offered thrips nymphs. Moreover, a high escape rate was observed when prey was considered suboptimal for development and reproduction. The predatory behaviour and prey preference were examined in the second experimental part. The predation rate of I. degenerans is generally low. Further, there is an absence of a strong preference for certain prey species. Based on the results of the laboratory experiments, it would be expected that I. degenerans is not a successful thrips predator. Nevertheless, I. degenerans has been used for many years in agricultural practice. Since the laboratory experiments carried out in the current study could not explain the control potential of this phytoseiid predator, further research may be warranted to fully understand its role in the regulation of arthropod pest populations