RP11 Expanding the range of uses of Phytoseiulus persimilis

The aim of this project is to investigate the ways in which to expand the range of crops and climatic conditions under which predatory mites can be used as biocontrol agents. By combining collection of wild populations with selective breeding we aim at producing strains that are insensitive to adverse climatic conditions, have increased reproductive rates, and accept more prey species.

The predatory mite Phytoseiulus persimilis is perhaps the best known example of a predatory mite species used for augmentative biological control. It was the first species to be reared and utilized at a mass-scale, and still is successfully applied to control spider mites around the world. Although P. persimilis is a very effective control agent for some species of spider mites on many host plants species, it is ineffective against some other damaging species and/or on some crop species. In addition, the use of P. persimilis is limited by its sensitivity to adverse climatic conditions. The main objective of this project is to exploit natural variation to expand the range of uses of P. persimilis.

We will use naturally existing genetic variation to select for desirable traits such as tolerance to adverse climatic conditions and unsuitable host plant species, acceptance of certain pest species as prey, and the foraging behaviour. Further improvements will be made by selective breeding. The PhD candidate will collect and maintain genetically variable strains of P. persimilis and design bioassays to quantify the relevant phenotypic variation. The candidate will develop a breeding and selection program for certain desirable traits. The performance of the new phenotypes will be compared to the existing commercial strains in (semi-) field tests. Finally, the stability of the new phenotypes in the mass-rearing will be studied.