EFFECTS OF LOW APPLICATION RATES OF THE PYRETHROID PP321 ON THE APPLE ORCHARD MITE COMPLEX (ACARI) IN ONTARIO

The impacts of the pyrethroid PP321 on the mite fauna in an apple orchard were studied at the Smithfield Experimental Farm of Agriculture Canada, Ontario, from 1988 to 1989. Two predacious mites, the phytoseiid Amblyseius fallacis (Garman) and the stigmaeid Zetzellia mali (Ewing), were affected by pyrethroid applications. The highest numbers of predators were found in untreated trees, and the lowest numbers were found in the trees treated with the higher rate of the pyrethroid (P < 0.05). Zetzellia mali has roughly the same susceptibility to PP321 as does A. fallacis. Two species of tetranychid phytophagous mites, the European red mite, Panonychus ulmi (Koch), and the twospotted spider mite, Tetranychus urticae Koch, were positively associated with pyrethroid applications. Significantly higher numbers of these mites were found in the pyrethroid-treated trees than in untreated ones (P < 0.05). Another phytophagous mite, the apple rust mite, Aculus schlechtendali (Nalepa) (Eriophyidae), was strongly suppressed by PP321 applications. Lower rate applications of the pyrethroid allowed more predators to survive, and resulted in lower abundances of tetranychid mites than did the higher rate. Therefore, reduced rates of pyrethroids may prove to be compatible with integrated control of spider mites in apple orchards.

A SURVEY OF PREDATORY MITES IN ONTARIO APPLE ORCHARDS WITH DIVERSE PESTICIDE PROGRAMS

Leaves were collected between 28 July and 10 September from 36 (1986) and 85 (1987) apple orchards, and examined for mites. Twelve species of Phytoseiidae were found: Amblyseius fallacis (Garman), Typhlodromus longipilus Nesbitt, A. andersoni (Chant), T. caudiglans Schuster, T. pyri Scheuten, T. pomi (Parrott), Phytoseius macropilis (Banks), T. herbertae Chant, A. driggeri Specht, A. finlandicus (Oudemans), T. conspicuus (Garman), and A. pusillus (Kennett), in order of frequency. The stigmaeid mites Zetzellia mali (Ewing) and Agistemus fleschneri Summers, a complex of erythraeid mites of Balaustium spp. and Hauptmannia spp., and tydeid mites, primarily Tydeus spp., were other common predatory species. Species of Tetranychidae, Bdellidae, Eriophyidae, Winterschmidtiidae, and Tarsonemidae, also were collected.Predatory mites were present each season in all abandoned orchards and in 43–74% of the commercial orchards. Their abundance in commercial orchards was compared with the use of insecticides applied only for control of the spotted tentiform leafminer, Phyllonorycter blancardella (Fabr.). Fewer (P < 0.05) phytoseiids occurred where pyrethroids were employed than in sites without pyrethroids, but differences were not found for similar use of the carbamoyl oxime, methomyl. Fewer (P < 0.05) stigmaeids occurred in sites treated with methomyl than in sites without methomyl, whereas such differences were not found for pyrethroid use.