Effect of biotic and abiotic factors on the incidence of aphid, Aphis craccivora Koch on cowpea

Abstract

Investigations were conducted on the “Effect of Biotic and Abiotic Factors on the Incidence of Aphid, Aphis craccivora Koch on Cowpea”. at Agronomy farm, of S.K.N. College of agriculture, Jobner (Rajasthan) during kharif, 2016. The aphid population commenced in the first week of August (31st SMW) and the first observation was recorded on 2nd August. Initially, population of aphid was (16.20 aphids/ three leaves). The population gradually increased and reached its peak in 34th SMW (108.13 aphids/ three leaves) when the minimum temperature, maximum temperature, mean relative humidity and rainfall was 24.40C, 30.50C, 84 per cent and 17.4 mm and gradually declined thereafter. The population of both the predators C. septempunctata and M. sexmaculatus were positively correlated (r = 0.82 and r = 0.72, respectively) with aphid population. The population of predators increased with the increase in aphid population. The correlation between population of C. septempunctata and M. sexmaculatus with abiotic factors viz., maximum and minimum temperature, mean relative humidity and rainfall had non significant correlation.