Seasonal incidence of mustard aphid, Lipaphis erysimi (Kalt.) on mustard crop

摘要

The severity of mustard aphid, Lipaphis erysimi, infestation in Brassica juncea [Indian mustard] crops and its period of occurrence were not uniform during two successive crop seasons (25th December 1989 to 6th March 1990, and 1st January to 13th March 1990) in India. Lipaphis erysimi occurred from the last week of December to the first week of March in 1989, and the first week of January to the second week of March in 1990. The peak infestation of L. erysimi (414.15 per 10 cm terminal shoot per plant) was recorded on 13th February in the first year, while the maximum infestation (471.10 per 10 cm terminal shoot per plant) was recorded on 6th February. The variable fluctuation in pest numbers during the two cropping seasons was attributed to climatic conditions.