Assessment of Amblyseius fallacis (Acari : Phytoseiidae) for biological control of tetranychid mites in an Ontario peach orchard

We introduced a mass-reared pyrethroid-resistant strain of the predatory ph ytoseiid mite Amblyseius fallacis (Garman) into an Ontario peach orchard in an attempt to control populations of the phytophagous mites Panonychus ulm i Koch and Tetranychus urticae Koch (Acari: Tetranychidae). Releases of 1,0 00 and 2,000 mites per tree were made, at three different times. The releas e of 2,000 mites per tree in June and in July resulted in significantly hig her phytoseiid densities than was observed on control trees. However, densi ties of P. ulmi or T. urticae were not significantly affected by any releas e rate or by timing. The release of 1,000 A. fallacis per tree, or of any d ensity in August, did not significantly increase phytoseiid abundance. In t he following year, population dynamics of both phytoseiid and phytophagous mites were not significantly affected by the previous year's release. Ambly seius fallacis can be a useful predator in some fruit orchards. However, fu rther research is necessary into the timing and rate of release, modified s pray programmes, and with different crops, in order to clarify the role of this species for biological control in Ontario peach orchards.