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ThesisItem Open Access Impact of habitat manipulation and biorationals on major insect pests of cabbage and their natural enemies(CCS HAU, Hisar, 2022-07) Jeevan B G; Kalkal, DeepikaStudies were carried out on habitat manipulation and effect of biorationals on major insect pests of cabbage and their natural enemies during Rabi, 2021-22 at HAU, Hisar. The experiment was carried out to access the impact of different cropping patterns, viz., T1 [cabbage + coriander as border crop], T2 [cabbage + mustard as border crop], T3 [cabbage + marigold as border crop], T4 [cabbage +fenugreek (3:1)], T5 [cabbage + marigold (3:1)], T6 [cabbage + fennel (2:1)] T7 [cabbage + coriander (2:1) + fennel as border crop], T8 [cabbage + mustard (2:1) + fenugreek as a border crop] and T9 [Control (Cabbage as sole crop)] on three insect pests viz., mustard aphid, diamondback moth and cabbage butterfly and two natural enemies viz., coccinellids and syrphid fly. Results on habitat manipulation revealed that lowest mean population of aphid and cabbage butterfly was found in T8 with 8.10 aphids/plant and 3.47 larvae/plant, respectively while highest in T6 with 13.38 aphids/plant and 5.13 larvae/plant, respectively whereas, DBM larval population was found lowest in T7 with 0.61 larvae/plant and highest in T3 [cabbage + marigold as border crop] with 1.15 larvae/plant. For increasing the population of coccinellids and syrphid fly treatment T7 was found best with highest population 3.44 coccinellids/plant and 1.57 maggots/plant, respectively. Aphid population shows significant positive correlation with morning relative humidity and negative correlation with maximum temperature and coccinellid population. Larval population of DBM (P. xylostella) showed significant positive correlation with maximum temperature and negative correlation with morning and evening relative humidity. Cabbage butterfly, P. brassicae larvae population showed significant positive correlation with maximum temperature and evening relative humidity and negative correlation with morning and evening relative humidity and aphid population. Syrphid fly maggot population also showed significant negative correlation with evening relative. Maximum cabbage yield (180.62 q/ha) was recorded in the treatment T2 with third highest B:C ratio (2.46) while the first highest B:C ratio (3.38) was observed in T5. Results of bio-efficacy of eleven treatments (nine biorationals and one chemical along with unsprayed control) revealed that malathion 50 EC (as check) recorded maximum per cent reduction over control against both mustard aphid (62.24 %) and diamondback moth (52.14 %). Among biorationals, L. lecanii (1x108cfu/g) and azadirachtin 0.15% exhibited maximum per cent reduction over control against mustard aphid and DBM with 53.75 % and 47.66 %, respectively. However, maximum population of coccinellids (2.52 coccinellids/plant) and syrphids (0.76 maggots/plant) was recorded in L. lecanii(1x108cfu/g) and (B. thuringiensis var. kurstaki 0.5 % WP), respectively. Maximum yield of 198.69 q/ha was recorded in malathion 50 EC whereas the highest yield among biorationals was recorded in L. lecanii (1x108cfu/g) with 186 q/ha. The benefit cost ratio for efficacy was found highest (2.58) in treatment malathion 50 EC followed by L. lecanii (1x108cfu/g) with B:C ratio 2.36 and azadirachtin 0.15% with B:C ratio 2.20. The control had the lowest benefit cost ratio, B:C (1.72).