Effect of ambient environmental conditions on the level of infestation by pulse beetle on different legumes

Pulses (grain legumes) are the second most important group of crops worldwide. Globally, 840 million people are under nourished mainly on account of inadequate intake of proteins, vitamins and minerals in their diets. Under stored conditions , pulses suffer maximum grain loss due to dreaded stored grain bruchid pests. Studies on the biology of pulse beetle Callosobruchus chinensis (Linn) (Coleoptera: Bruchidae) on the stored pulses revealed multi climatic factors particularly temperature can extend or reduce the life cycle of insects and thermal thresh hold influence the insects cycle stage, growth or some internal metabolic activities. In addition to temperature insects also respond to a-biotic factors like humidity, light and food etc. in different ways. The damage caused by the insect differ depending upon the seasons. Infestation was higher during the rainy season and lowest during the winter. The average number of eggs laid per female was found to be maximum when insect were reared at 30˚C and minimum number of eggs was observed at 15˚C in all host pulses. The highest number of eggs were noted laid on kidney bean (175.35) at 30˚C. The most favorable humidity level for adult emergence was found 75±5 per cent, at which maximum adult emergence of 121.32 occurred from cow pea. The combined effect of relative humidity and temperature showed that maximum grain weight loss at 30˚C and 85±5 per cent relative humidity while minimum weight loss at 15˚C and 65±5 per cent relative humidity. Thus, fundamental to insect growth, however, are environmental factors of temperature, relative humidity and moisture content of food materials. When a combination of favorable factors leads to increased insect development there is a co-related increase in the damage to materials through eating, despoiling, burrowing and other activities.