Population dynamics of potential bioagents of mustard aphid, Lipaphiserysimi(Kaltenbach) on different cultivars of rapeseed-mustard

Abstract

Field experiment was conducted to study the population dynamics of potential bioagents of mustard aphids on 9 different cultivars which included: Brassica alba cv. PSB-I, Eruca sativa Mill cv. T-27, Brassica campestriscv. BSH-I, Brassica napuscv. Sheetal, B. carinataBraun cv. CCN-06- 1, B. junceaL. cv. Varuna, B. nigraKoch. cv. PBR-I, Brassica campestriscv.YST-151 and Brassica campestriscv. PT-30. Population of aphid and natural enemies was recorded at weekly intervals. The results indicated that the first appearance of coccinellids and syrphids has been observed during 4th standard week, which gradually build up population and attained peak during 9th (pooled mean 1.42 coccinellids/ plant and 0.122 syrphid larva/plant) and 8th standard week (pooled mean 3.96 coccinellids/plant and 0.228 syrphid larva/plant) in 2008-09 and 2009-10 respectively, followed by a declining trend in the following weeks. Similarly first appearance of parasi-tization has been found to occur from 4th standard week followed by a gradual increase in the following weeks with maximum parasitization on PT-30 (33.32%) and BSH-1 (35.25%) during 2008-09 and 2009-10 respectively. Correlation between abiotic factors and these natural enemies was also studied. It has been observed that with the increase of aphid population the population of natural enemies also increased. The population dynamics of mustard aphids and its natural enemies var-ied according to climatic situations and between host plant species. So by computing population trends of both natu-ral enemies and aphids with meterological records would generate information on relative abundance and would certainly help in formulating sound pest management strategies against mustard aphid.