Compatibility of spinosad with predacious mites (Acari:Phytoseiidae) used to control western flower thrips (Thysanoptera:Thripidae) in greenhouse crops

Releases of predacious mites are recommended for use in greenhouse flower crops for suppression of western flower thrips, Frankliniella occidentalis (Pergande). Control from predacious mites alone, however, is not adequate and must be supplemented with the use of insecticides. The principal material currently used by growers in the northeastern United States for western flower thrips control is spinosad (Conserve (R)). In laboratory tests on direct toxicity, we found that fresh residues (2 h) of this material were not toxic to motile stages of Neoseiulus (=Amblyseius) cucumeris (Oudemans) (74 vs 78% survival for the treated group and the untreated water controls, respectively), the principal species of predacious mites used for control of western flower thrips, but did lower survival of Iphiseius degenerans (Berlese) (56 vs. 73% survival for the treated group and the untreated water controls, respectively). There were no differences for either species from exposure to older (24 h) residues. In contrast, using the same assay we observed 10 and 3% survival of first instar and adult western flower thrips. We found no indication of that either mite species was repelled by freshly dried (2 h post application) residues of this compound. Spinosad did, however, reduce oviposition of mites when confined in glass vials with pollen, a water source, and pesticide-treated foliage. Oviposition in the first 24 h period after confinement was not affected but in the second and third days, it was reduced by 48 and 76% for N. cucumeris and 41 and 70% for I. degenerans, compared with oviposition in the same periods by mites in untreated vials. These data indicate that the use of spinosad may not be compatible with releases of these predacious mites in a western flower thrips suppression program.