Chakraborty, M.K.KHALKHO, ARBIND ROSHAN2018-01-172018-01-172017http://krishikosh.egranth.ac.in/handle/1/5810039530STRATEGIC MANAGEMENT OF INSECT PESTS OF LINSEED (Linum usitatissimum L.) WITH PARTICULAR REFERENCE TO LINSEED BUD FLY, (Dasyneura lini Barnes)Linseed (Linum usitatissimum L.) is an important oilseed crop after rapeseed and mustard grown in India. Its yields have remained stagnant for many years due to many factors, of which losses caused due to insect pests particularly the linseed bud fly (Dasynrura lini Barnes) are supposed to be of prime importance. Considering the significance of linseed crop and damage caused by insect pests including the linseed bud fly (D. lini), a field trial was carried out during rabi, 2014- 15 to develop effective management practices against the insect pests. Altogether five sets of filed experiments were undertaken, in addition to, general pests monitoring work which were conducted during, 2014-15. Altogather, seven insect pest species were recorded during rabi, 2014- 15. However, the of incidence of Helicoverpa armigera (1.67 - 3.00/ 5 plants), Caliothrips indicus (6.00 - 10.33/ 5 plants), Amrasca kerri Pruthi (7.33- 9.33/ 5 plants), Laphygma exigua Hub. (0.33 - 1.67/ 5 plants) and Pentatomid bug (Piezodorus hybneri Gmel) (9.00 to 14.00 / 5 plants) was well within the tolerable limit (i.e. < 10%). The linseed bud fly (0.8 – 2.15 maggots/ bud) emerged as the major pest. Linseed harboured as many as five natural enemies, viz., Lacewings (Chrysoperla spp.), Lady bird beetle (Coccinella spp.), Rove beetle (Paederus spp.), Praying mantis (Mantodea) and Yellow wasp (Polistes spp.), all being predatory in feeding habit. However, their population was negligible. The important weather variables viz., temperature (maximum and minimum), relative humidity (morning and afternoon) correlation studies had been done.There was a found to be significant positive correlation between the bud fly infestation with maximum and minimum temperatures and positive correlation coefficient done of both morning and afternoon relative humidity. Findings of the varietal screening revealed that out of seven cultivars/ variety tested, R 552 recorded lowest bud fly infestation of 17.95 and 24.68 per cent at green and dough stages, respectively, which was much lower than the susceptible check Neelum (29.71 and 39.32 per cent). In another experiment, six insecticides were tested against untreated control on linseed bud fly as well as other pests of linseed. Each treatment was applied at fifty per cent flowering time. The grasshopper (1.00 to 1.67 per 5 plants), linseed capsule borer (1.67 to 3.00 per 5 plants), thrips (6.00 to 10.33 per 5 plants), jassid (7.33 to 9.33 per 5plants), linseed caterpillar (0.33 to 1.67 per 5 plant)s, pentatomid bug (9.00 to 14.00 per 5 plants) appeared in less number and were considered as minor / stray pests. The number of linseed bud fly maggots ranged from 0.80 to 2.15 per bud and caused significant loss. The mean of bud fly infestation was least (7.78 %) in the treatment Imidacloprid followed by Fipronil (7.88 %). The treatment Imidacloprid also recorded highest (11.60 q / ha) grain yield followed by Fipronil (10.90 q / ha). The highest cost: benefit ratios was to be recorded in Imidacloprid (1: 54.92) followed by Diafenthiuron (1: 13.72). The results on impact of intercrops on linseed bud fly infestation indicated that the combination linseed + gram (4:2) recorded the lowest (15.46 %) infestation followed by linseed + gram (5:1) where the infestation recorded was 19.40 per cent. Linseed when grown with intercrops, lentil and pea recorded about 49 per cent increase in yield over linseed (sole) crop. However, linseed+ gram (4:2) gave the highest yield and there was a yield increase of 65.05 per cent as compared to linseed sole crop.en-USnullThesis