1Department of Entomology, Rajendra Agricultural University Pusa, Samastipur-848 125, Bihar (India).
2Department of Entomology and Agricultural Zoology, Tirhut College of Agriculture, Rajendra Agricultural University, Dholi (Muzaffarpur)-843 121, Bihar (India).
Natural populations of both the bean aphid (Aphis craccivora Koch.) and its coccinellid predators reacted sharply to the changing weather factors like temperature and relative humidity but almost in opposite direction. These weather parameters collectively accounted for a wide fluctuation in aphid population from 31.55 to as high as 99.96 per cent depending upon the crop type (lentil, Lathyrus and faba bean) and the phase of the pest population (ascending, oscillating and descending phase). The combined effects of these two weather parameters on predators populations varied in magnitude from 82.43 to 99.00 per cent. A highly significant and positive associationship existed between the natural population of the pest and the predators on all these three crops. Daily rate of population change values for both the pest and predators and the numerical relationship between their fluctuating populations on Lathyrus as well as lentil established an ecologically poor synchrony in their activities. The coccinellid community comprised as many as seven species, viz., Coccinella septempuncta Linn., Coccinella septempunctata var. divaricata Oliv., Coccinella sp., Coccinella transversalis Fab., Micraspis disorder Fab., Menochilus sexmaculatus Linn., and Menochilus sp., and their populations were collectively considered in evaluating prey-predator relationship.
