Quadraspidiotus perniciosus Comstock

Quadraspidiotus perniciosus is a serious pest of apple in north-western India. It has also been recorded on other deciduous trees, poplars and willows. About 50 hosts have been recorded in India. The scale insect colonizes all parts of the plant. Young tree bark when attacked show characteristic deep red or purplish stain. The bark of old tree develop cracks and exude large amount of gummy substance. The fruits attacked may also develop reddish spots around the scale infestations. In case of severe infestation the attacked tree may get defoliated. Such trees do not bear any fruits. The over-wintering nymphs become active in mid-March; the males emerge in April. The female reproduces in mid-May producing in a month 200 to 400 nymphs each. The crawlers settle in a day or two on the bark and secrete waxy covering in about 4 days. They become mature in 20 days. The life cycle is completed in 35-40 days. The scale insect passes through 4-5 generations before mid October when hibernation starts.

The scale insect is multiplied on pumpkins (Cucurbita maxima Dend) in a rearing facility where temperature (27°C) and humidity (65% RH) are controlled. The initial culture is obtained from the field and reared separately. The predators, hyperparasitoids and diseases if any are eliminated. Once the pure culture is established, the host multiplication is started. The crawlers of the scale insect are collected from the mother culture and dusted over the fresh pumpkins placed on a plastic rim in a cage (45 cm3). The infested pumpkin is ready for exposure to the San Jose scale parasitoids from 12th day of infestation. At least 10% of the crawler infested pumpkins from each lot are used for continuation of the host insect culture.