Department of Entomology, N.D. University of Agriculture and Technology, Kumarganj, Faizabad-224 229, Uttar Pradesh (India).
*Present address: Entomologist, Horticultural Experiments & Training Centre, Chaubattia-263 651, Ranikhet, Almora, Uttar Pradesh (India).
The severity of mustard aphid, Lipaphis erysimi (Kalt.) in mustard (Brussica juncea L.) crop and its period of occurrence were not uniform in two successive crop seasons. The population count of mustard aphid at weekly intervals revealed two kinds of fluctuating trends during both the crop seasons. Mustard aphid occurred in rabi crop from the last week of December to the first week of March in the first year. Its incidence in the second year was from the first week of January to second week of March. The peak infestation of mustard aphid (414.15/10 cm terminal shoot/plant) was recorded on 13th February in the first year, while its maximum infestation (471.10/10 cm terminal shoot/plant) was recorded on 6th February in the next crop season. The variable fluctuation in two crop seasons was observed largely due to climatic conditions.
