Biology and predation of the Japanese strain of Neoseiulus californicus (McGregor) (Acari: Phytoseiidae)

Abstract

The life history characteristics and predation of the Japanese Neoseiulus californicus (McGregor) strain on the two-spotted spider mite, Tetranychus urticae Koch, were studied in the laboratory under 60–70% RH and 16L: 8D conditions. Developmental time from egg to adult emergence decreased when temperature increased. Total development period of immature stages was longest at 15°C and shortest at 35°C for both male and female. Sex ratio favored females and temperature did not exert a critical effect on sex determination. The total degree-days required from egg to adult female were 71.43 degree-days with thermal constant of 10.64°C. At 25°C, female laid a total of 34.73 eggs during 17.91 days of oviposition period. The net reproductive rate (Ro) was highest at 25°C (22.92 females/female) and lowest at 30°C (16.74 females/female). The mean generation time (T) decreased from 20.61 to 16.79 days with increasing temperature up to 30°C. The intrinsic rate of natural increase (rm) ranged from 0.162 to 0.285, and was maximal at 25°C. A gravid N. californicus female consumed more eggs, larvae and nymphs than adult male or female of T. urticae. As T. urticae density increased, prey consumption likewise increased. However, increasing the number of adult male or female preys did not increase the number of eggs laid by a female predator. The results were used to assess the effectiveness of the Japanese N. californicus strain as an important biological control agent against T. urticae.