Physico-chemical parameters of pulses affecting the bruchid (CALLOSOBRUCHUS CHINENSIS LINN.) infestation

Members of the family Bruchidae (Coleoptera) are important pests of a variety of seed material. The adults oviposit on stored seeds or on developing seedpods in the field. The larval and in most species, the pupal stages are completed within the seed and the adult eventually emerges through a small exit hole. Due to this mode of development bruchids are easily transported along with the seed material from one country to another thus spread very quickly. Forty-eight species of bruchids have been recorded from different localities of India. Out of these, 23 species belong to Bruchidius, 8 to Caryedon, 5 to Callosobruchus, 4 to Spermophagus, 2 each to Bruchus, Conicobruchus and to Specularius and 1 each to Zabrotes and Sulcobruchus. As many as 13 species are associated with edible seeds especially pulses. The genera Callosobruchus restrict their activities to the stored pulses. In the North-East India three species i.e., C. chinensis, C. maculatus and C. analis are abundant and they feed on several hosts such as green gram, red gram, cow pea, bengal gram, grass pea, pea, lentil, black gram and moth bean. Amongst these, C. chinensis is the most serious pest in the Terai agro-climatic region of West Bengal. Studies revealed that relative preference of C. chinensis to different pulses vary widely depending upon their physical and chemical characteristics. Ovipositional preference was dependent on the seed color, seed texture, seed weight, thickness of seed coat, seed moisture and various chemical parameters. Concentrations of phenol, OD phenol and protein were studied in chemical investigations. Studies on correlation between the physico-chemical characters of different legumes on ovipositional behaviour, adult emergence and total developmental period of the insect revealed that moisture content of seeds, single geed weight and seed coat thickness had negative correlation with oviposition, adult emergence percentage and total developmental period while phenol content, OD phenol content and protein content had positive correlation with oviposition and developmental period while negative correlation with adult emergence percentage.