Bio-efficacy of different insecticides against thrips infesting groundnut (Arachis hypogaea L.)

Introduction

Groundnut or peanut A. hypogaea L. (Fab.) is a valuable cash crop for millions of small scale farmers in the semi-arid tropics and is the principal oilseed crop in India. The word groundnut (A. hypogaea Linn.) is derived from the Greek word "Arachis" meaning legume and "hypogaea" meaning below ground. It is commonly known as peanut, monkey-nut and goobernut. Groundnut is native to South America. The crop can be grown successfully in areas receiving rainfall from 600 mm to 1200 mm. The best soil for the groundnut crop is sandy loam, loamy and medium black Anonymous (1990) [1] . The plant suffers from the ravages of insect pests and a loss in production both in terms of quantity and quality. As many as 52 species of insect pests and two species of mites have been recorded infesting the groundnut crop in India Singh et al. (1990) [2] . Among these insect pests infesting groundnut crop in Gujarat, the thrips are considered a key pest. The important species include Scirtothrips dorsalis Hood, Frankliniella shultzeri Trybom and Thrips palmi Karny. The damage caused by thrips depends on the population of damaging stage of an insect, crop growth stage, cropping pattern in the area and prevailing environmental conditions Patel and Patel (1983) [3] . Thrips are known to transmit bud necrosis disease in groundnut, which has been widely reported from different states of India such as Tamil Nadu, Karnataka, Andhra Pradesh, Maharashtra, Gujarat, Rajasthan and Madhya Pradesh Amin (1984) [4] . The chemical management of insect-pests is most practiced by the groundnut farmers for the management of thrips. However, the continuous and indiscriminate use of insecticides has led to the development of resistance in thrips populations. In recent years, several new insecticide molecules and combination products have become available in the market. Therefore, it is necessary to evaluate the efficacy of these insecticides against thrips in groundnut.

Materials and Methods

A field experiment was conducted at Main Oilseeds Research Station, Junagadh Agricultural University, Junagadh during the summer, 2022 & 2023 to check the efficacy of different insecticides against thrips in summer groundnut using a Randomized Block Design (RBD) with three replications. The first spray of the respective insecticides was applied at the initiation of thrips infestation and second at10 days after first spray.

The data on population of thrips were recorded on three trifoliate leaves (top, middle and bottom canopy of the plants) per plant by randomly selecting five plants from each net plot. The pre-treatment observation was recorded at one day before spray and post treatment observations were recorded at 3, 7 and 10 days after each spray. Pod and haulm yield was recorded at harvest. Statistical analysis was carried out using ANOVA (Panse and Sukhatme, 1985) [5] .

Results and Discussion

The population of thrips was found homogenous in all treatments before spray as treatment differences were nonsignificant (Table 1). The thrips population before spray ranged from 5.45 to 6.94 thrips/trifoliate leaves/plant. The population of thrips recorded after three days of spray, indicated that spinetoram 11.7 SC; 0.012% performed better than other insecticides and recorded the significantly lowest (1.36 thrips/trifoliate leaves/plant) thrips population which was statistically at par with spinosad 45 SC; 0.014% (1.63 thrips/trifoliate leaves/plant) and cyantraniliprole 10.26 OD; 0.010% (1.78 thrips/trifoliate leaves/plant). The next better treatments were thiamethoxam 12.6 + lambda-cyhalothrin 9.5 ZC; 0.007%, pyriproxyfen 10 + bifenthrin 10 EC; 0.020% and imidacloprid 19.81 + beta-cyfluthrin 8.49 OD; 0.01% in which thrips populations were observed 2.63, 3.46 and 3.62 thrips/trifoliate leaves/plant. More or less similar trend was observed after seven and ten days of first spray. Pooled over period data of second spray (Table 3) indicated that the lowest (0.64 thrips/ trifoliate leaves/plant) population of thrips was recorded in treatment of spinetoram 11.7 SC; 0.012% which was statistically at par with spinosad 45 SC; 0.014% (0.76 thrips/trifoliate leaves/plant) and cyantraniliprole 10.26 OD; 0.010% (0.90 thrips/trifoliate leaves/plant) after three days of second spray. The next treatment in the order of effectiveness was thiamethoxam 12.6 + lambda-cyhalothrin 9.5 ZC; 0.007% (1.35 thrips/trifoliate leaves/plant) pyriproxyfen 10 + bifenthrin 10 EC; 0.020% (1.39 thrips/trifoliate leaves/plant) and imidacloprid 19.81 + beta-cyfluthrin 8.49 OD; 0.01% (1.49 thrips/trifoliate leaves/plant). The treatment of afidopyropen 50 DC and lambda-cyhalothrin 5 EC remained least effective among all other insecticides evaluated which showed 2.05 and 2.27 thrips/trifoliate leaves/plant, respectively. More or less similar trend was observed after seven and ten days of second spray. The present finding is more or less in conformation with the reports of earlier workers who reported that spinosad 45% SC; 0.014% proved significantly more effective and recorded lowest thrips (0.79 thrips/trifoliate leaves/plant) in groundnut Bhut et al. [6] . Spinosad 45% SC; 0.014% was most effective against chilli thrips Shinde et al. [7] . Spinosad 45 SC @ 200 ml /ha, thiamethoxam 25 WG @ 100 g /ha was very effective against thrips on groundnut at Kadiri Anonymous [8] . Application of spinetoram reduces the population density of T. tabaci infesting garlic plants and gave the highest yield Hussein et al. [9] . Treatment of spinosad 45 SC recorded a higher yield (t/ha) compared to the other treatments Patil et al. [10] .

Yield and Economics

The pod and haulm yield in different insecticidal treatments varied from 1590 to 2600 kg/ha and 2621 to 3832 kg/ha, respectively (Table 4 and5). The highest (2600 kg/ha) pod yield was recorded in the plot treated with spinetoram 11.7 SC; 0.012% and it was at par with spinosad 45 SC; 0.014% (2288 kg/ha) and cyantraniliprole 10.26 OD; 0.010% (2248 kg/ha). The highest (41255 Rs./ha) net realization was obtained in the treatment spinetoram 11.7 SC; 0.012% followed by spinosad 45 SC; 0.014% (31442 Rs./ha) and cyantraniliprole 10.26 OD; 0.010% (25213 Rs./ha) (Table 5).

Acknowledgement

AcknowledgementsThe authors gratefully acknowledge the support of Research Scientist (Groundnut), Main Oilseeds Research Station and Director of Research, Junagadh Agricultural University, Junagadh, Gujarat, India for providing vital resources needed for the successful execution of this study.

References

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