Incidence, transmission, host range and population dynamics of aphids transmitting bean common mosaic virus of cowpea

Cowpea Vigna unguiculata (Linn.) Wilczek is an important pulse crop which belongs to family Fabaceae. Bean Common Mosaic is a major viral disease in cowpea resulting in significant yield losses to a tune of 70 per cent. The results showed that disease was widespread in all the surveyed areas, with the highest average per cent disease incidence being observed in Bagalkote (29.82%) followed by Vijayapur (27.41%), Dharwad (25.47%) and Belagavi district (18.89%). The disease incidence varied from 3.25 per cent to 69.56 per cent among the villages and from 12.94 per cent to 44.80 per cent among the taluks. The host range and transmission studies revealed that BCMV infecting cowpea is readily transmissible by sap, aphids and through seeds. The mechanical transmission was 71.43 per cent, aphid transmission was found to an extent of 54.42 per cent and the seed transmission of BCMV infecting cowpea was 64.00 per cent. The population of aphid (Aphis craccivora) was maximum during the 38th and 39th Standard Meteorological Weeks (SMWs) with the mean value of 92.70 and 81.20, respectively. The aphid population varied at different crop stages. Aphid population build up showed a strong significant negative correlation with rainfall. There was a significant negative correlation with minimum temperature and morning RH.