Rahman, K.A., Sapra, A.N., 1940.
Biology of the mite Paratetranychus indicus Hirst, a pest of sugar cane in the Punjab. Indian Journal of Entomology, 2 (2): 201-212.
Abstract
Paratetranychus indiens, Hirst, all stages of which are described, is widely distributed in India and is a serious pest of sugar-cane in the Punjab, where it also feeds on Sorghum vulgäre and S. halepense. As many as 30 overlapping generations were observed in the course of a year; all stages occur together and breeding is continuous. The oviposition period lasted 10-15 days from April to September, and 17-39 days during March and October-December, and the daily and total numbers of eggs deposited by females under observation were 1-7 and 35-69. During April and May the females died immediately after they had finished ovipositing, but in June-November they survived for a further period of 1-6 days. Males died within 4 days of mating, but unpaired examples survived for up to 12 days in March-September and 20 in October and November. The egg stage lasted 21/2-3 days in April-September, 5-13 days in March and October-December and 29 days in January. The larval, protonymphal and deutonymphal stages in males and females each lasted 11/2-3 and 3-5 days, respectively, in April-September, 41/2-8 and 6-11 days in March and October or November, and 13-19 and 16-24 days in December-February. Some males, however, passed through only two instars. Parthenogenesis is common, 94-96 per cent, of the eggs laid by unfertilized females giving rise to males. Females are somewhat more numerous than males, but the ratio is almost 1: 1 in May. Infestation is spread by wind and, in fields of sugar-cane and S. vulgare, where the leaves touch each other, by mites crawling from plant to plant. Adult males of P. indicus feed very little, and the chief damage is caused by the females and immature stages. During summer, the latter can survive starvation for 8 hours, females for 24 hours and males for 72. Feeding by the mites causes the formation of red patches, which increase in size and spread over the entire leaf, which finally falls. This red coloration is probably caused by the injection into the leaf during feeding of a toxic substance that reacts with the plant sap. The mite is present on Sorghum halepense throughout the year. It spreads to S. vulgare and sugar-cane in May, and is active on them until July, when the monsoon rains kill all stages except the egg. Further damage is caused to S. vulgäre in September-November, but the leaves of sugar-cane are too .tough to be infested at this time. Soft-leaved varieties of sugar-cane were more susceptible to attack those having hard leaves.
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