Seasonal abundance of spider mites and their predators on red raspberry inQuebec, Canada

Seasonal abundance of spider mites and their predators on red raspberry was studied in 1993 and 1994 at 2 agricultural locations near Quebec City, Can ada. Three raspberry systems, wild raspberry, pesticide-free cultivated ras pberry, and commercial raspberry treated with a variety of pesticides, were sampled at frequent intervals. Tetranychus mcdanieli McGregor accounted fo r 87.5, 80.6, and 95.0% of the identified spider mites collected in the com mercial, untreated, and wild systems, respectively. Tetranychus urticae Koc h was observed in low numbers in both years. Spider mites were more abundan t in the commercial and untreated systems than in the wild system, and ther e was generally no difference between commercial and untreated systems in 1 993, whereas in 1991 there was more spider mites in the commercial system t han in the untreated one. Predatory mites were present in all systems. Ambl yseius fallacis (Garman) was the most abundant predator in the commercial s ystem, whereas a complex of other predatory mites species dominated the wil d system. The coccinellid Stethorus punctillum Weise was abundant in the un treated system and rare in the commercial and the wild systems. Variations of predator abundance among treatments did not correlate with variations of spider mite abundance, and could be explained by seasonal predator-prey as ynchrony.