Biology of Callosobruchus theobromae (L.) (Coleoptera: Bruchidae),a seed pest of edible legumes


Abstract: Bruchids are cosmopolitan in distribution and completely associated with wild andcultivated legumes worldwide. These chunky beetles spoil the valuable share of legume proteinswhich otherwise be eaten by human being, thus competing with the normal life of the mankindespecially in the developing countries, where per capita consumption of animal protein is verylow. Callosobruchus theobromae (L.) (Coleoptera: Bruchidae) infests developing pods and seedsof Dolichos lab lab L. syn. Lablab purpureus (L.) Sweet throughout the year and extended itshost range on other legume commodities in the stores. Adult breeds a few hours after theiremergence and gravid females preferred egg laying directly on seeds and some time on pods also.First instar larvae hatched out from a fertilized egg and bored vertically into the host seed forsuccessive juvenile development, unless infected by idiobiont and koinobiont parasitoids. Uninfestedhealthy larva undergo different moults inside the host seed and emerged an adult insectafter cutting an exit hole in seed coat from inside. This inner mode of infestation protects the pestspecies from fluctuating environment and toxic pesticides and also responsible for their dispersalin new locality due to anthropogenic import and export seed consignments. Perusal of literaturerevealed that C. theobromae is a pest of D. lab lab, but present investigations have unveiled itspest status on other edible legumes viz. Glycine max (L.) Merr., P. aureus Roxb. and V. sinensis(L.) Walp. also. Developmental compatibility on different legume commodities and number ofgenerations completed in a year are also explored. Studies have been extended to observe thephenotypic variations and phase dimorphism exhibited by pest species during different seasons ofa year.

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