Bioefficacy studies of biorational approaches against Leucinodes orbonalis Guenee on brinjal in Himachal Pradesh
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Date
2023-01-16
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CSK HPKV, Palampur
Abstract
Studies were carried out to know the incidence of Leucinodes orbonalis on brinjal in agro-climatic
zone I and II of Himachal Pradesh and data on the incidence of L. orbonalis were recorded at monthly
interval during 2019 and 2021. The crop was found to be infested with L. orbonalis at all the locations
during both the years. Incidence of L. orbonalis appeared early in the month of May and remained up
to the end of the season. The peak incidence of L. orbonalis was recorded in the month of July and
August on shoots and fruits of brinjal during both the years. Among all the locations, Una district had
a maximum shoot and fruit infestation (25.33 and 28.83%, respectively) during 2019, while in 2021
the maximum shoot infestation was recorded in Hamirpur district (26.50%) and fruit infestation in
Kangra district (28.64%). The intrinsic toxicity studies against neonate larvae of L. orbonalis revealed
emamectin benzoate as most toxic with LC50 value of 0.0043 ppm followed by spinosad (0.0303
ppm), Bacillus thuringiensis (3.989 ppm), azadirachtin (8.847 ppm), Brahmastra (24203.194 ppm)
and Agniastra (29795.95 ppm). The field experiments were undertaken during the kharif season of
2020 and 2021 at the Experimental Farm of the Department of Entomology, CSK Himachal Pradesh
Krishi Vishvavidyalaya, Palampur. For the management of L. orbonalis, different approaches were
evaluated under three modules, cultural & mechanical methods (M1), natural products & biopesticides
(M2) and insecticides (M3). In Module 1, amongst seven treatments, minimum mean shoot infestation
(9.33%) and fruit infestation (number as well as weight basis i.e., 12.68 and 13.86%) was recorded in
neem cake (NC) + clipping of shoots. In Module 2, out of nine treatments, application of Bt resulted
in least mean shoot infestation (13.56%), whereas fruit infestation on the number basis was minimum
in neem cake + Azadirachtin; on the weight basis, neem cake + Bt recorded lowest per cent fruit
infestation (15.27%). In case of Module 3, shoot infestation was minimum (6.40 %) in emamectin
benzoate followed by neem cake + emamectin benzoate (6.70%) and spinosad (6.87%). On the basis
of fruit infestation (number and weight), neem cake + application of emamectin benzoate resulted in
lowest fruit infestation (9.39 and 8.85%) followed by emamectin benzoate (9.61 and 8.88%). On the
basis of incremental output input ratio of two years, emamectin benzoate (27.27) was the most
economically viable treatment followed by spinosad (10.82). After two applications of insecticides,
the average initial deposits of emamectin benzoate (@10 g a.i./ha) were 0.307 ppm, whereas the
average initial deposits of spinosad (@75 g a.i./ha) were 0.489 ppm. A waiting period of 4 days for
emamectin benzoate and 2 days for spinosad was suggested for safe consumption of brinjal fruits.