Effect of Certain Environmental Factors on the Biology of Mango Fruit Weevils (Curculionidae:Coleoptera)

Sternochetus mangiferae (Fabr.) (mango stone weevil) and S. gravis (mango pulp weevil) are the serious pests of mango fruits in Manipur. The effect of certain environmental factors, especially temperature, relative humidity and rainfall, has been studied on the duration of their life cycle under the laboratory conditions during February 1987 to July 1989. The duration of life cycle of these weevils has been observed to vary from season to season. The longest duration (55 days) of the life cycle has been observed during 1988, and the shortest duration during 1987. The environmental parameters have been observed to play a vital role on the biology of these fruit weevils. An average temperature of 28°C and relative humidity of 72.77% have been found favourable for the longer life cycle whereas the average minimum temperature of 26.44°C with 74.66% relative humidity has been observed to shorten their life cycle.