Effect of fruit fly protein bait on the red scale parasitoid, Aphytis lingnanensis (Hymenoptera: Aphelinidae): attraction and toxicity

Abstract

AbstractProtein bait spray is a tool used widely in tephritid fruit fly pest (Diptera: Tephritidae) control and eradication programs. However, this technique might have a negative effect on non‐target, beneficial insects. Aphytis lingnanensis is a very successful parasitoid of the California red scale, Aonidiella aurantii, a worldwide pest of citrus. Though A. lingnanensis is widely used in augmentative release programs, the impact of protein bait‐insecticide mixtures on the parasitoid is not documented. In this study, we investigated the attraction of A. lingnanensis to Pinnacle® protein, a fruit fly protein bait commonly used in Australia. Following this, the contact toxicity of field weathered residues of protein bait mixed with the insecticides spinosad, fipronil, malathion and chlorpyrifos to A. lingnanensis were evaluated. Finally, the non‐lethal impact of these residues on the capacity of A. lingnanensis to parasitize its host was investigated. Food‐deprived parasitoids were not attracted to protein but were significantly attracted to honey. The lack of attraction of protein, however, increased when sugar was added to it. Relative to a control of only protein, protein bait‐insecticide mixtures applied on citrus leaves and weathered outdoors for 2 h, 3 days, 7 days and 12 days caused high mortality of A. lingnanensis. The residual toxicity of the four weathering periods, for all the protein bait‐insecticide mixtures, produced high mortality rates varying between 90% and 100%. In addition, the capacity of A. lingnanensis to parasitize its host after exposure to weathered residues containing an insecticide was severely affected. The results suggest that A. lingnanensis is highly susceptible to the insecticides evaluated here when used in fruit fly protein baits. Therefore, the use of these insecticides in protein bait sprays, as part of an area wide fruit fly management, should be carefully considered in areas where augmentative release and conservation of A. lingnanensis are also applied.