Assessment of yield losses in Mustard (Brassica juncea L.) due to Mustard Aphid (Lipaphis erysimi Kalt.) under different thermal environments in Eastern Central India

摘要

Mustard aphid (Lipaphis erysimi.Kalt.) has been reported as one of the devastating pests inrealizing the potential productivity of Indian mustard (Brassica junceaL.). The experiment was carriedout to assess the yield losses in mustard due to mustard aphids grown in different thermal environmentsunder protected and unprotected conditions. To provide different thermal environments the crop wassown on 5 dates i.e. 08, 18 and 28 November and 08 and 18 December during winter seasons of 1995-96, 1996-97 and 1997-98. It was observed that yield attributes and yield of mustard was significantlydecreased in delayed sowing even under protected conditions. On an average maximum seed yield of1409 kg/ha was harvested when the crop was sown on 08 November under protected condition, whileonly 279 kg/ha seed yield was recorded under unprotected condition. Similarly the yield attributes andyields drastically reduced under unprotected condition as compared to protected one in all the thermalenvironments. On the mean basis 80.6, 81.4, 95.2 and 97.6 per cent yield loss was observed under unpro-tected condition as compared to protected condition in 08, 18, 28 November and 08 and 18 Decembersowing, respectively. It was also observed that the critical period of mustard exposure to aphids wasfound to be the 3r dweek after aphid appearance when the crop was in flowering stage and hence the con-trol measures have to be initiated before flowering. There was not much difference in natural aphid population/plant in the crop sown up to end of November while the aphid population increased sudden-ly in December sown crop