DEVELOPMENTAL TIMES AND OVIPOSITION RATES OF PREDATORY MITES TYPHLODROMUS-PYRI AND AMBLYSEIUS-ANDERSONI (ACARI, PHYTOSEIIDAE) REARED ON DIFFERENT FOODS

The developmental times and the reproduction of two resistant Italian strains of Typhlodromus pyri Scheuten and Amblyseius andersoni (Chant) were studied in the laboratory by rearing them on the spider mites Panonychus ulmi (Koch) and Eotetranychus carpini (Oud.), on the eriophyid Colomerus vitis (Pgst.) and on pollen of Mesembryanthemum criniflorum. The response of T Pyri and A. andersoni females to a spider mite supply (P. ulmi or E carpini) of 4, 8 and 16 adult female prey per female predator per day was also studied. Development of T. pyri on E. carpini and C. vitis required a shorter period than on M. criniflorum pollen, while intermediate values were recorded for P. ulmi. When the highest number of prey was offered, the influence of different foods on oviposition rates of T. pyri was not significant. An increase in spider mite supply favoured a shorter pre-oviposition period and higher oviposition rates. Development of A. andersoni was faster on pollen than on spider mites, while intermediate values were found concerning C. vitis. Differences statistically significant were recorded for development on P. ulmi and C. vitis. Colomerus vitis proved to be the more suitable food in terms of oviposition. The oviposition rate decreased when feeding upon P. ulmi, but reached intermediate values on E. carpini and M. criniflorum. Increasing spider mite densities caused shorter pre-oviposition times and higher oviposition rates. Using a given number of E. carpini females, rather than those of P. ulmi, resulted in higher oviposition rates and shorter pre-oviposition times. For both predators, the results suggest a higher intrinsic rate of population increase on E carpini or C vitis than on P. ulmi.