BIOLOGICAL-CONTROL OF APPLE MITES BY A PHYTOSEIID MITE COMPLEX AND ZETZELLIA-MALI (ACARI, STIGMAEIDAE) - LONG-TERM EFFECTS AND IMPACT OF AZINPHOSMETHYL ON COLONIZATION BY AMBLYSEIUS-ANDERSONI (ACARI, PHYTOSEIIDAE)

Long-established populations of Typhlodromus pyri Scheuten were less common in plots in 1993 with dense Zetzellia mali (Ewing) than in plots with Z. mali than without, but less difficulty than Metaseiulus occidentalis (Nesbitt) had had in 1992. Newly released Z. mali did not establish well in a plot that had T. pyri only, but Z. mali seemed to be displacing T. pyri after 4 yr in some mixed-species release plots of M. occidentalis and T. pyri. After immigration from nearby vegetation to apple, colonization by Amblyseius andersoni (Chant) was less in azinphosmethyl-treated plots than in similar untreated plots. Colonization by A. andersoni was greatest in plots with few T. pyri or Z. mali or both but some occurred in all plots not sprayed in 1993 (those originally receiving no releases, single or mixed-species releases of T. pyri, and M. occidentalis in 1990). Colonization by A. andersoni was greatest where M. occidentalis had been displayed in 1991 or 1992 by Z. mali. Results are discussed in relation to long-term biological control and more biologically based integrated pest management.