Population dynamics of soybean girdle beetle (Obereopsis brevis Swedenbord) in soybean crop

Introduction

Soybean (Glycine max L. Merrill), a member of the family Fabaceae, is one of the world's oldest and most economically significant leguminous crops. Widely recognized as the "golden bean" or "miracle crop," it serves as the foremost global source of vegetable oil and plant-based protein, thereby making an indispensable contribution to food, nutritional, and economic security. In India, soybean has emerged as a commercially important oilseed crop owing to its remarkable adaptability, high productivity, and multifaceted industrial applications. It ranks among the country's leading oilseed crops after groundnut and mustard and constitutes a vital component of the agricultural economy. Nutritionally, soybean is exceptionally rich, containing nearly 40% high-quality protein and approximately 20% oil, along with essential amino acids, vitamins, minerals, and carbohydrates. Furthermore, its ability to fix atmospheric nitrogen through symbiotic association with Rhizobium enhances soil fertility, reduces dependence on chemical fertilizers, and promotes sustainable agricultural production (Swathi et al., 2020; Dugje et al., 2009) [1,2] . Globally, soybean production is dominated by Brazil, which contributes approximately 169 million metric tonnes, accounting for nearly 40% of the world's total production. The United States occupies the second position with about 118.84 million metric tonnes (28%), followed by Argentina with 50.9 million metric tonnes (12% Therefore, the present investigation was undertaken to evaluate the extent of damage caused by major insect pests in relation to prevailing weather parameters, with the objective of generating scientific insights that support predictive pest forecasting and environmentally sustainable crop protection under changing climatic conditions (Swathi et al., 2020) [1] .

Materials and Methods

The 1). The highest infestation coincided with elevated daytime temperatures, negligible rainfall, and comparatively dry atmospheric conditions, indicating that warm and moisture-deficient environments substantially enhanced pest proliferation. Correlation analysis for 2024 further substantiated the influence of climatic variables on girdle beetle incidence. Maximum temperature exhibited a strong and highly significant positive correlation with stem girdler damage (r = 0.803), suggesting that elevated daytime temperatures promoted pest development and feeding activity. Conversely, minimum temperature showed a weak and non-significant positive relationship (r = 0.054 NS), indicating its limited contribution to pest population dynamics. Average relative humidity demonstrated a highly significant negative correlation (r = -0.904), while rainfall also exhibited a significant negative association (r = -0.667), confirming that humid and rainy conditions suppressed pest incidence, either by directly affecting insect survival or by enhancing the activity of natural enemies and entomopathogens ( 2). The correlation analysis for 2025 revealed a slightly different response of the pest to individual weather parameters. Maximum temperature exhibited a weak and non-significant positive correlation (r = 0.168 NS), indicating that daytime temperature alone was not a decisive determinant of pest abundance during this season. In contrast, minimum temperature showed a strong and highly significant negative correlation (r = -0.850), suggesting that lower night temperatures favored girdle beetle activity (Table 3.0). Similarly, average relative humidity (r = -0.846) and rainfall (r = -0.821) displayed highly significant negative correlations with pest incidence, reaffirming that increased atmospheric moisture and precipitation effectively suppressed population build-up. Similarly, Kumawat et al., (2010) [4] reported girdle beetle infestation initiation in 32 nd SM. and Kumar et al., (2020) [3] also reported girdle beetle infestation start in the 32 nd SMW. Similarly Panwar et al., (2021) [5] also reported infestation of girdle beetle was started in 31 st SMW, thereafter the increasing trend of infestation of the girdle beetle was observed and it continued up to 38 th SMW. The maximum infestation of plants due to girdle beetle was observed during 39 th SMW. Panwar et al., (2021) [5] reported that maximum temperature had exhibited a positive correlation with infestation of girdle beetle.

References

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2. Dugje IY, Omoigui LO, Ekeleme F, Bandyopadhyay R, Lava Kumar P, Kamara AY. Farmers' Guide to Soybean Production in Northern Nigeria. Ibadan, Nigeria: International Institute of Tropical Agriculture; 2009. p. 21.
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5. Panwar A, Nayak MK, Tomar DS. Population dynamics of major insect pests of soybean and their correlation with abiotic factors in Bundelkhand agroclimatic zone of M.P. Journal of Entomology and Zoology Studies. 2021;9(1):1824-1827.