ENTOMOPATHOGENICITY OF PHOTORHABDUS BACTERIA AGAINST PULSE BEETLE, CALLOSOBRUCHUS CHINENSIS L. (BRUCHIDAE: COLEOPTERA) IN CHICKPEA GRAINS

Abstract

Pulse beetle, being cosmopolitan is responsible for severe losses in lentil, maize, cowpea,
mung bean and sorghum. In chickpea, 50 to 60 percent losses in seed weight and 46 to 66 percent protein
losses have been recorded due to severe attack of Callosobruchus chinensis. Indiscriminate use of
pesticides and fumigants to control pulse beetle has resulted in insecticide resistance, environmental
hazards, residual toxicity and pest resurgence so the control trends have been changed and particularly
biological control measures have attained high significance like entomopathogenic bacteria were used as
alternate bio-control agents against this serious pest. During this research the pathogenicity of
entomopathogenic bacteria Photorhabdus temperate was observed against pulse beetle at different
concentrations. Bacterial culture was grown in Luria broth agar at 25°C in incubator, and then it was
multiplied in neutralized distilled water medium to get single colonies of bacteria on this medium.
Initially, concentrations 8×107 and 5.6×107 cells/ml of P. temperate were obtained by counting no. of
cells using spectrophotometer. After that we diluted these bacterial concentrations into required
concentrations like 1×106, 1×107 and 1×108 cells/ml. The concentration 1×108 cells/ml was reported as
the highly efficient in controlling the fecundity with the minimum 4.82 eggs/grain. The least number of
F1adults (12.1) was observed at this bacterial concentration. The same concentration showed minimum
damage in terms of holes development in grains. Results revealed that the higher concentrations were
more effective than the lower concentrations of entomopathogenic bacteria. The findings of the research
provided an effective and safe biological control measures and in future will lead to an effective IPM
programme for this economic pest.