Relative Abundance of Turnip Aphid and the Associat ed Natural Enemies on Oilseed Brassica Genotypes

Abstract

A two-year field study was conducted at Punjab Agri cultural University, Ludhiana, India, to study the relative abundance of mustard/t urnip aphid, Lipaphis erysimi (Kaltenbach) (Hemiptera: Aphididae) and the associa ted resident natural enemies on 10 different rapeseed-mustard genotypes which included : Brassica juncea : RH 7846, RH 9501, RK 9501, JMM 927, Purple Mutant; B. napus : Hyola PAC 401 (Hybrid); B. rapa ecotype yellow sarson cv. YST 151; B. rapa ecotype brown sarson cv. BSH 1; B. carinata : DLSC 2 and Eruca sativa : T 27. The objective was to study whether indigeno us natural enemies can be used for biological control of musta rd aphid. Population of turnip aphid and different natural enemies was recorded at weekl y intervals. There was lack of synchronization in the peak activity of natural ene mies with that of the aphids with a time lag of one to two weeks depending upon the genotype . For example, on B. juncea cv. RH 7846, the peak aphids’ population was recorded duri ng the 10 th Standard Meteorological Week (SMW) while that of predators’ was recorded du ring the 12 th SMW in 2007-2008 crop season. Among the different natural enemies, c occinellids were the most abundant with grubs being dominant in the initial phase of p opulation development and adults in the later one. There is a need to conserve the resi dent natural enemies in mustard ecosystem for effective early season suppression of the aphid population or release them early in the season to suppress aphid population in lag phase of its development. Keywords: A groecosystem, Ecology, Mustard aphid, Parasitoid, P redator.