Great Basin Naturalist


The only San Jose scale parasite found at two sites in northern Utah was a uniparental form of Aphytis vandenboschi DeBach & Rosen. Parasites overwintered as pupae and were attracted to San Jose scale pheromone traps. Mature female scales were most heavily parasitized, although some prepupal males and instar II female scales were attacked. Only partial development occurred between 11.7 and 18.3 C, and fecundity was reduced between 28 and 31 C. Based on 11.7 C, 460 degree days were required in the field and 410 degree days at 26 C in the laboratory per generation. By the end of the season during 1981 at Brigham City, 30.9% of the adult scales on twigs and 79.2% on leaves were parasitized. During 1982, parasitism was 21.1% on twigs and 70.9% on leaves. A mite, Pyemotes herfsi (Oudemans), was a major predator of Aphytis in both laboratory cultures and field populations.