Optimal rearing medium for the population growth of the predatory mite, Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae)

Background: The successful rearing of predators or parasitoids is one of the most important elements in biological control programs. The dried fruit mite, Carpoglyphus lactis (L.), can be used as an alternative prey for the phytoseiid predatory mite, Amblyseius swirs0kii (Athias-Henriot). Main body: This study aimed to evaluate the suitability of 3 different diets for C. lactis when rearing A. swirskii: brown sugar, baker’s yeast, and the mixture of brown sugar and baker’s yeast along with 3 initial predator:prey ratios (1:7, 1:12, and 1:20). After 30 days, both the baker’s yeast and the mixture of brown sugar + baker’s yeast diets resulted in the highest predator densities (40.5 times increase at an initial predator:prey ratio of 1:20, with the baker’s yeast diet), whereas the mixture diet produced the highest density of prey. The brown sugar resulted in the lowest number of predator and prey mites. This may be due to lower feeding and predation rates of the prey and the predator mites on the brown sugar medium since its relative moisture content and adhesiveness inhibits mite movement. The final predator:prey ratio was also highest on the baker’s yeast diet. Conclusions: This study demonstrated that the population growth of A. swirskii was the highest when C. lactis was reared on baker’s yeast.