Population development of turnip aphid Lipaphis erysimi (Kaltenbach, 1843) (Hemiptera: Aphididae) and the associated predator Coccinella septempunctata Linnaeus, 1758 as affected by changes in sowing dates of oilseed Brassica.

The effect of sowing date of Indian mustard crop, Brassica juncea (L.) Czern. on turnip aphid, Lipaphis erysimi (Kaltenbach, 1843) incidence and population build up of adults and larvae of its predator, the seven spotted lady bird beetle, Coccinella septempunctata Linnaeus, 1758 was studied by keeping five sowing dates viz. October 10, October 20, October 30, November 10 and November 20. The aphid incidence was found significantly lowest (12.5 aphids/plant) in plots sown on October 10 as compared to plots sown on November 10 (39.3) and November 20 (58.0) but it was on a par with plots sown on October 20 (14.4) and October 30 (14.1). Significantly highest larval population (1.4 and 1.2 larvae/plant) of C. septempunctata was recorded in crop sown on November 10 as compared to other sowing dates. However, significantly highest adult population of 2.0 beetles/plant was recorded on crop sown on November 20 as compared to all other sowing dates. The implications of changes in sowing time with respect to management of the pest are discussed