Varietal screening against insect pest complex of chilli and their management through essential oils
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Date
2020-12, 2020-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Screening of commonly grown chilli varieties against chilli thrips. To study the influence of crop phenological characters against insect pests of chilli crop and to assess the relationship between them.To assess the effectiveness of plant derivatives against insect pests of chilli. To study the antifeedant activity of plant derivatives against Spodoptera litura and Helicoverpa armigera, these studies were conducted during the rabi seasons in the year 2018-19 and 2019- 2020 under field and laboratory conditions at Pantnagar, Uttarakhand. Among the fifteen commonly grown chilli varieties that were screened against thrips population and leaf curl index (LCI) Pant C-1 recorded minimum thrips population and LCI and it was categorized as moderately resistant. Seven varieties were grouped as moderately susceptible and seven varieties were susceptible. Proline (6.00 micro moles/ g leaf to 4.00 micro moles/ g leaf) and phenol content (15.22 mg/ 10 g leaf to 9.57 mg/ 10 g leaf) were negatively and highly significantly associated with thrips population while protein (7.71 mg/ 10 g leaf to 14.38 mg/ 10 g leaf) and total sugars (25.40 mg/ 10 g leaf to 50.33 mg/ 10 g leaf) were positively and highly significantly associated with thrips population. All the insect pests had positive and highly significant association with plant height. Leaf area had a positive but non significant effect on insect pest population. Number of branches/ plant had a negative and non significant effect with aphids, whitefly, fruit borer, Spodoptera and Coccinella. Number of leaves/ plant had negative and highly significant impact on insect pests and predator population. Petiole length and Internode length had a highly significant while a negative and positive impact on insect pests and predator population. The arthropod diversity was recorded in “Pusa Jwala” variety of chilli. Fifteen species of insect pests, fifteen species of natural enemies and one species of pollinator were recorded from chilli field. Population fluctuation of insect pest was also correlated with abiotic factors where a
positive correlation of aphids (r= 0.503* and 0.440*) and thrips (r= 0.393 and 0.421*) was observed with mean temperature. During 2018-19 mean relative humidity had a positive and non significant impact on insect pest and predator population while a negative association was observed in 2019-2020. During both the crop season rainfall was positively associated with pest and predator population. However, sunshine hours was positively associated with pest population during 2018-19 and negatively associated with pest population during 2019-2020. Multiple regression equation was also calculated during both the season. In the year 2018-19 the weather factors caused a variation in the range of 43% to 64% in insect pests and predator population while in 2019-2020 variation of 32% to 53% was observed. Three simultaneous application of Fipronil 200 SC @ 150 ml/ha was found to be most
effective in managing all insect pest population. Maximum predator population was observed in the untreated plots followed by plots treated with Linseed oil @ 5%. Overall yield was maximum in Fipronil 200 SC @ 150 ml/ha treatment (7.63 T/ha). The highest cost benefit ratio was obtained in the plots treated with Linseed oil @ 5% (1:0.54 and 1:0.48). The antifeedant activity of essential oil was also calculated against Spodoptera litura and Helicoverpa armigera under laboratory conditions. The mean leaf area consumed by both the larvae (Helicoverpa armigera and Spodoptera litura) was minimum in rosemary oil @ 2% (2.64
cm2) treatment followed by citronella oil @ 2% (3.20 cm2).Maximum leaf area was consumed in untreated control (14 cm2) followed by linseed oil @ 2% (10.26 cm2).