Survival and dispersal of young larvae of Chilo partellus (Swinhoe) (Lepi-doptera: Pyralidae) in two cultivars of sorghum

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Abstract
The establishment and survival of larvae of Chilo partellus (Swinh.) on two sorghum cultivars in the six days after hatching was investigated in the field in India. During this period relatively few larvae are present outside the whorls of the plants, and the numbers present six hours and three days after hatching are proportional to the numbers hatching. The number of larvae in the plants declines during these first three days, but subsequently is stable. Some dispersal to adjacent plants occurs during this period and, at the plant spacing used, approximately seven plants were infested by larvae from a single egg-mass of 40 eggs. The relative susceptibilities of the two cultivars, IS 1151 and IS 2205, altered with the age and size of the plants. This is a vulnerable period in the life-history of the insect and attention should be focused on it in developing resistant cultivars, but because the susceptibility of the plants changes with age it is important to decide the age at which protection would have the greatest economic value.