TOXICITY OF A NUMBER OF PESTICIDES TO STRAINS OF TYPHLODROMUS-PYRI AND AMBLYSEIUS-ANDERSONI (ACARI, PHYTOSEIIDAE)

Side effects of ten pesticides used in orchards and vineyards were tested with a laboratory method on several Dutch and Italian strains of the predatory mites Typhlodromus pyri Scheuten and Amblyseius andersoni (Chant). Resistant and susceptible strains of both species were studied. Results showed that a test which evaluates mortality of various developmental stages and fecundity of adult females is better than one that measures only survival of adult females. A definite resistance to certain pesticides was found in Italian T. pyri and A. andersoni. The level of resistance to parathion, azinphos-methyl and carbaryl was particularly high in some strains of A. andersoni. The high level of resistance to certain pesticides was often associated with a marked reduction in fecundity.