Studies of a uniparental form of Aphytis vandenboschi (Hymenoptera: Aphelinidae), a parasite of the San Jose scale in northern Utah.
Aphytis vandenboschi, a parasitoid of San Jose scale [Quadraspidiotus perniciosus], was studied in the laboratory at temperatures between 10 and 31°C, 47% RH and LD 16:8, and in apple orchards in Utah in 1981 and 1982. Parasitoids overwintered as pupae and were attracted to Q. perniciosus pheromone traps. Mature female scales were heavily parasitized, although some prepupal males and 2nd-instar females were attacked. Only partial development occurred at 11.7-18.3°C, and fecundity was reduced at 28-31°C. With a threshold of 11.7°C, 460 and 410 day-degrees/generation were required in the field and laboratory at 26°C, respectively. At the end of the 1981 season, 30.9% of adult diaspidids on twigs and 79.2% on leaves were parasitized. During 1982, parasitism was 21.1% on twigs and 70.9% on leaves. Pyemotes herfsi was a major predator of A. vandenboschi in both laboratory cultures and field populations.