Habitat structure and its influence on populations of Amblydromalus limonicus (Acari: Phytoseiidae)

Abstract

Cannibalistic behaviour can be a limitation in mass rearing where predator-predator competition can be high. However, increasing habitat structural complexity has been shown to reduce cannibalism through a reduction in encounter rates and the provision of more refuge and oviposition sites. This study investigated the use of different rearing media and its ability to mitigate cannibalism in the predatory mite Amblydromalus limonicus (Garman & McGregor). The rearing substrates tested were buckwheat husks, gorse husks, rice husks, vermiculite, and wheat bran, which were compared against a control treatment with no substrate. These laboratory experiments were done in two different relative humidities (70% and 85%) with both water and pollen (Typha orientalis Presl) supplementation. The rearing media had a strong significant effect on populations of A. limonicus while humidity did not. Rice husk was found to hold the highest populations of the predator, whereas the control and wheat bran treatments had the lowest. The higher populations associated with the rice husk treatment were attributed to a decrease in encounter rates, the provision of additional shelter and oviposition sites, and low mould infestation. Issues with sampling bias, effects of mould in the system, and potential applications of rice husk are discussed.