Synergism of Plant Oils with Different Insecticides against Pod Borer, Helicoverpa armigera (Hubner) Hardwick Infesting Chickpea

Background: Gram pod borer, Helicoverpa armigera (Hubner) Hardwick has developed high level of resistance against so many insecticides due to some operational and biotic factors. The resistance can be managed by many ways among which adding of plant materials in insecticidal solution, which is having a synergistic effect, is one of the better ways to overcome this problem. Methods: In aim to break the resistance of insecticides towards this pest, an experiment was carried out to know the synergistic effect of different plant oils along with different insecticides against pod borer infesting chickpea at Junagadh Agricultural University, Junagadh (Gujarat) during two consecutive years i.e ., 2017-18 and 2018-19. The experiment was laid in randomize block design having nine treatments (two oils and three insecticides) along with control. Result: The results revealed that the minimum (10.98 %) pod damage was observed in the treatment of chlorantraniliprole 18.5 SC 0.006% + neem oil 0.5% which was found at par with flubendiamide 48 SC 0.015% + neem oil 0.5% (12.04 %). As far as the yield and economic is concern, highest (2634 kg/ha) yield and net realization (57,008 Rs /ha) was recorded in the treatment of chlorantraniliprole 18.5 SC 0.006% + neem oil 0.5% followed by flubendiamide 48 SC 0.015% + neem oil 0.5% (2432 kg/ha and 45,934 Rs/ha ). The highest (1:10.33) ICBR was obtained in the treatment of chlorantraniliprole 18.5 SC 0.006% + neem oil 0.5% followed by chlorantraniliprole 18.5 SC 0.006% (1:9.36) and flubendiamide 48 SC 0.015% + neem oil 0.5% (1:7.13).


INTRODUCTION
Pulses are important group among the food crops which occupies a unique position in the world of agriculture by virtue of their high protein content. Among all the pulses, chickpea (Cicer arietinum Linnaeus) is one of the important pulses grown in rabi season which is commonly known as "Bengal gram" or "Gram" and mainly grown in the Indian subcontinent. In India, the area under chickpea is 9.99 mha with a production of 11.91 mT with productivity of 1192 kg/ha during 2020-21 (Anonymous, 2023a. In Gujarat, the area under chickpea is 7.64 lakh hectares with a production of 13.91 lakh tonnes with productivity of 1820 kg/ha during 2022-23 (Anonymous, 2023b. Insect pests are probably the main factor limiting the grain legume yields. More than 150 species of insects are known to attack pulse crops in India and out of these, about 25 causes serious damage to monsoon and winter pulse crops (Bindra, 1968). Among the different pests infesting chickpea crop, Helicoverpa armigera (Hubner) Hardwick (Lepidoptera: N octuidae) is a c osmopo litan and polyphagous pest, which attacks numerous crops of agricultural importance, which feeds voraciously from seedling stage to maturity and causes about 70-80 per cent damage to the chickpea (Khare and Ujagir, 1977;Setiyawati et al., 2000). Lal et al. (1986) estimated an annual loss of about 203 crore of rupees in chickpea in India. As per the report of ICRISAT, losses caused by H. armigera on chickpea and pigeon pea fields exceeded Rs.12,000 millio/year (Anonymous, 1996).
Looking to the economic importance of this pest, farmers are using several old /newer chemicals to combat the attack of pod borer. As per the feedback of farmers regarding management of H. armigera, it is difficult to manage with well known insecticides viz., quinalphos 0.05%, indoxacarb 0.015%, spinosad 0.018%, chlorantraniliprole 18.5 SC @ 0.006 etc. Probable reason behind this is gram pod borer has developed high level of resistance against so many insecticides due to some operational and biotic factors in Gujarat. The resistance can be managed by many ways. Among various ways, adding of plant materials in insecticidal solution, which is having a synergistic effect, is one of the better ways to overcome this problem.

MATERIALS AND METHODS
The experiment was laid in randomize block design having nine treatments (Table 1) along with control to know its efficacy against Helicoverpa armigera in chickpea crop at Department of Entomology Farm, Junagadh Agricultural University, Junagadh during during two consecutive years i.e., 2017-18 and 2018-19. Chickpea, cultivar GJG-5 was grown as per standard agronomical practices having 45  10 cm spacing and plot size of 4.0  2.7 m (gross) and 3.6  1.8 m (net) for each treatment. The first application of combination was applied when pest crossed its ETL (0.75 larvae/plant before flowering and 0.5 larvae/ plant after flowering) and next sprays was given at 20 days interval. Sticker has been added @ 3 ml/10 lit. of water in each treatment during each spray. For recording the observations on numbers of eggs and larvae /plant, per cent pod damage, ten plants were selected randomly from each plot and observations were recorded prior as well as 3, 7 and 14 days after spraying of the combination. The yield and economics were also worked out. The pesticide residues were also carried out for effective treatment.

RESULTS AND DISCUSSION
Pooled data of both the years (Table 2 and 3) on synergistic effect of different insecticides and plant oils after 3 days of first spray revealed that the lowest (2.51) eggs/plant was observed in the treatment of chlorantraniliprole 18.5 SC 0.006% + neem oil 0.5%. It was found statastically at par with flubendiamide 48 SC 0.015% + neem oil 0.5% (2.60 eggs/plant). The next better treatments were flubendiamide 48 SC 0.015%, chlorantraniliprole 18.5 SC 0.006% and spinosad 45 SC 0.018% + neem oil 0.5% which was also statistically at par with each other. More or less similar trend was observed after 7 and 14 days of first spray as well as 3, 7 and 14 days after second spray.
As far as the larval population is concern (Table 4), the synergistic effect of different insecticides and plant oils after 3 days of first spray revealed that the lowest population of 3.12 larvae/plant was observed in the treatment of chlorantraniliprole 18.5 SC 0.006% + neem oil 0.5%. It was found statistically at par with flubendiamide 48 SC 0.015% + neem oil 0.5% (3.24 larvae/plant). The next better treatments were flubendiamide 48 SC 0.015%, spinosad 45 SC 0.018% + neem oil 0.5% and chlorantraniliprole 18.5 SC 0.006% which was also statistically at par with each other. More or less similar trend was observed after 7 and 14 days of first spray as well as 3, 7 and 14 days after second spray ( Table 5).
The pooled data on chickpea pod damage (Table 6) revealed that the minimum (10.98%) pooled pod damage was observed in the treatment of chlorantraniliprole 18.5 SC 0.006 % + neem oil 0.5% which stood statistically at par with flubendiamide 48 SC 0.015% + neem oil 0.5% (12.04%). The pooled data on chickpea yield (Table 7) was found significantly differed in all the treatments over control.
Looking to the results, it is clearly exposed that due to heavy insecticidal spray of newer molecules leads to development of resistance in H. armigera and thus an approach of mixing of oils having synergistic effect i.e., neem oil, sesame oil etc. can break the resistance and also useful in managing such notorious pest. However, some research on effect of insecticides on H. armigera were reviewed and results on bio-efficacy of each treatments were are in close conformity with the obtained results as the application of neem           oil (300 ppm) was found efficient in suppressing the population of H. armigera in chickpea with respect to benefit cost analysis (Ramteke et al., 2002). As per the report of Landge et al. (2013), rynaxypyr 20 SC @ 40 g a.i./ha was most effective in reducing larval population followed by flubendiamid 20 WDG @ 50 g a.i./ha. Chavan et al. (2014) recorded the minimum larval incidence of H. armigera (0.95 and 0.36 larva/ meter row length) in rynaxypyr 20 SC at 3 and 7 days after spraying, respectively, followed by flubendiamide 48 SC (1.47 and 0.78 larvae/MRL). According to Jayanth and Kumar (2022), chlorantraniliprole 18.5% SC + neem oil was found good treatment against gram pod borer with lower mean larval Synergism of Plant Oils with Different Insecticides against Pod Borer, Helicoverpa armigera (Hubner) Hardwick Infesting Chickpea