Impact of habitat manipulation and biorationals on major insect pests of cabbage and their natural enemies
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Date
2022-07
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CCS HAU, Hisar
Abstract
Studies 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).