Dr. G. M. ParmarBavisa R. V.2018-07-062018-07-062018-06http://krishikosh.egranth.ac.in/handle/1/5810057848Present investigations on population dynamics, yield loss and field efficacy of chemical insecticides against Lipaphis erysimi (kalt.) in mustard were carried out at Main Oilseeds Research Station, Junagadh Agriculture University, Junagadh during Rabi season, 2016- 17 Aphid population commenced from 4th Week After Sowing (WAS) [1st week of December (49th Standard Meteorological Week- SMW)] with aphid index 0.14 and reached to peak (4.9 aphid index/plant) at 15th week after sowing i.e., 3rd week of February (8th SMW). Thereafter, decreasing trend was observed up to 2nd week of March (11th SMW) as crop reached to its maturity. Relatively higher activity (1 to 4.90 aphid index/plant) was observed during 2nd week of January to 4th week of February (2nd to 9th SMW) i.e. 9th to 16th WAS. However, at the maturity of the crop, the negligible population with more number of winged aphids was observed on green stem of mustard. The correlation matrix indicated that the aphid population had highly significant positive correlation with evaporation (r = 0.627**) and significant and positive relation with minimum temperature (r = 0.514*). Aphid population had positive correlation with bright sunshine hours (0.349), wind speed (0.470), maximum temperature (0.405), mean temperature (0.471), and growing degree day (0.471) while negative relationship with morning relative humidity (-0.452), evening relative humidity (-0.334) and mean relative humidity (-0.423). The avoidable loss in yield of mustard due to mustard aphid, L. erysimi estimated 60.70 per cent. The yield recorded in protected plot was 1559 kg/ha which ………………………………………………………...………….………….Abstract showed 191.94 % yield increase over control while unprotected plot recorded 825 kg/ha. Testing the bio-efficacy of insecticides, thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015% flonicamide 0.02% and imidacloprid 0.005% successfully checked the incidence of aphid. The next best treatments were clothianidin 0.003%, dimethoate 0.03% and thaicloprid 0.024%. Among the tested insecticides, the highest aphid index was noted in plots treated with dinotefuran 0.008 % and it was less effective treatment among all the evaluated insecticides and was at par with fipronil 0.05 % and imidacloprid 40% + fipronil 40% @ 0.03%. The order of effectiveness of synthetic insecticides was thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015 % > flonicamide 0.02% > imidacloprid 0.005 % > clothianidin 0.003 % > dimethoate 0.03% > thiacloprid 0.024 %> imidacloprid 40% + fipronil 40% @ 0.03% > fipronil 0.05 % > dinotefuran 0.008 %. The maximum yields was found from the plots treated with thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015% (1690 kg/ha) followed by flonicamide 0.02% (1439 kg/ha), imidacloprid 0.005% (1279 kg/ha), and clothianidin 0.003% (1259 kg/ha). The plots treated with the dinotefuran 0.008% (842 kg/ha) recorded the lowest yields. The chronological order of various insecticidal treatments in comparison to control based on yield (kg/ha) was: thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015% > flonicamide 0.02% > imidacloprid 0.005% > clothianidin 0.003% > dimethoate 0.03% > thiacloprid 0.024% > imidacloprid 40% + fipronil 40% @ 0.03% > fipronil 0.05% > dinotefuran 0.008%. The maximum net realization was obtained from the treatment of thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015 % (39590 Rs/ha) followed by flonicamide 0.02% (30303 Rs/ ha) and imidacloprid 0.005% (24383 Rs/ha).The highest ICBR (16.93) was calculated from the plots treated with imidacloprid 0.005% followed by dimethoate 0.03% (15.79) and proved to be more economical insecticide, while fipronil 0.05% (1.10) recorded lower ICBR and proved to be the least economical insecticidal treatment In nutshell, based yield and economics; imidacloprid 0.005% was found to be the most effective and economical insecticidal treatment followed by dimethoate 0.03%, flonicamide 0.02%, thiamithoxam 12.6% + lambda cyhalothrin 9.50% @ 0.015%. Thus, it can be recommended for the management of aphid in mustard.enENTOMOLOGYPOPULATION DYNAMICS, YIELD LOSS AND FIELD EFFICACY OF CHEMICAL INSECTICIDES AGAINST Lipaphis erysimi (Kalt.) IN MUSTARD 2569Thesis