Investigations on insect dynamics in Indian mustard at different sowing dates

The results indicated that the population of insect-pests particularly mustard aphid increased as the sowing got delayed and maximum population of mustard aphid was recorded on the crops sown on 10^th December. In the case of natural enemies, syrphid (hover fly) maggot was recorded as the predominant and was present on almost all the aphid colonies. Seed yield of mustard was reduced in delayed sowing. Maximum yield was recorded in plots sown on 10^th November. Delay in sowing influenced both the population of mustard aphid (93 to 96%) and seed yield (92 to 93%). Mustard crop (Brassica juncea) should be sown within first fortnight of November.