Studies of the predatory miteAmblyseius victoriensis (Acarina: Phytoseiidae) in citrus orchards in south-east Queensland: control ofTegolophus australis andPhyllocoptruta oleivora (Acarina: Eriophyidae), effect of pesticides, alternative host plants and augmentative release

Abstract

Seasonal history studies and a pesticide disruption trial showed that the Australian phytoseiidAmblyseius victoriensis (Womersley) was a very effective predator of the native eriophyidTegolophus australis Keifer, in commercial citrus orchards at Gayndah and Mundubbera, Queensland, from 1984 to 1990.Amblyseius victoriensis numbers rose from 10–20 per 100 leaves in spring to 100 or more per 100 leaves in mid summer, keeping the percentage ofT. australis-infested, fruit well below an economic threshold of 10%.

However, in the same orchards,A. victoriensis only controlled the cosmopolitan eriophyidPhyllocoptruta oleivora (Ashmead), when less than 5% of the fruit was infested with the pest and predator numbers exceeded 40 per 100 leaves.

Aspects of orchard management influencing populations ofA. victoriensis, were evaluated. The pesticides benomyl, dicofol, mancozeb, methidathion, and mezineb reduced populations by 100%, methomyl by 89%, chlorpyrifos by 80%, fenbutatin oxide by 42.5% and endosulfan by 27.5%. Iprodione and hydrated lime caused a 17% reduction, but copper oxychloride and narrow-range oil had little effect. Encouragement of alternative host plants in the orchard increased populations ofA. victoriensis. Where Rhodes grass.Chloris gayana Kunth, was allowed to flower in the inter-rows, its windblown pollen served as a supplementary food source. Windbreak rows ofEucalyptus torelliana F. Muell. acted as reservoirs ofA. victoriensis for nearby blocks of citrus. Augmentative release was effective for re-establishingA. victoriensis where it was absent following pesticide suppression.