A laboratory evaluation of the astigmatid mite Hemisarcoptes cooremani Thomas (Acari : Hemisarcoptidae) as a potential biological control agent for an armored scale, Aonidiella aurantii (Maskell) (Homoptera : Diaspididae)

The host stage and species utilized by a parasitic mite, Hemisarcoptes coor emani Thomas (Acari: Hemisarcoptidae), was studied to evaluate the mite's p otential as an augmentative biological control agent against California red scale, Aonidiella aurantii (Maskell) (Diaspididae: Homoptera). We compared how readily the mite established on five oleander scale, Aspidiotus nerii (Bouche), stages and eight red scale stages using no-choice experiments in which mites were offered a single scale stage and species. We also offered the mite a choice between two stages of the same species, a choice between oleander and red scale in the same stage, and a choice between oleander and red scale in the same two stages. We found that few mites established on s cales younger than second molt, but they readily established on the older o leander scale stages. They accepted gravid and parturient female red scale less readily than they did the same oleander scale stages. We suspect that the heavily scleratized body of California red scale attached to the cover in these stages prevented the mite from gaining access to the scale body on which to feed, Our results suggest that red scale is a poor-quality host f or the mite. Consequently, this predator/parasitoid is unlikely to be an ef fective augmentative biological control agent against A. aurantii in Califo rnia's San Joaquin Valley. The younger stages provide insufficient resource s for the mite to develop and reproduce and the older stages are too diffic ult to feed on. (C) 1999 Academic Press.