Biological control of Oligonychus perseae (Acari: Tetranychidae) on avocado: I. evaluating release timings, recovery and efficacy of six commercially available phytoseiids

Abstract

Releases of six different species of phytoseiid mites (Galendromus annectens, G. helveolus, G. pilosus, G. occidentalis, Neoseiulus californicus, and Typhlodromus rickeri) at a rate of 2000 per tree were evaluated for their ability to control Oligonychus perseae on avocados in California. We tested two different release timings (early and late) to determine the effect of prey density on predator establishment rates, predator population growth, and suppression of O. perseae. The early release was initiated when 25% of sampled leaves were infested with one or more adult O. perseae. We failed to recover predators four weeks after this release. A second early release was subsequently made when 75% of sampled leaves were infested with one or more adult O. perseae. Five out of six phytoseiid species were recovered following this release (G. pilosus did not establish). Densities of G. helveolus and N. californicus increased following the second early release and peaked 8 and 10 weeks post release, respectively. Late phytoseiid releases were made when 95% of sampled leaves were infested with O. perseae. Two predators, G. helveolus and N. californicus were recovered from late releases, and neither exhibited increases in density as O. perseae numbers were naturally declining at the time this release was made.