On-Farm Evaluation of Multi-mechanism Insecticidal Rotations for Suppressing the Pod Borer Complex in Blackgram (Vigna mungo L.)

Abstract

A multi-locational, four-year on-farm trial (OFT) was conducted from 2022 to 2025 across diverse rainfed environments in Maharashtra, India, to evaluate the bio-efficacy, economic sustainability, and field resilience of an advanced insecticide rotation module (T2) against the baseline Farmer's Practice (T1) for managing the blackgram pod borer complex. The targeted chemical sequence (T2) comprised monocrotophos 36% SL (625 mL/ha), chlorantraniliprole 18.5% SC (100 mL/ha), profenofos 50% EC (700 mL/ha), and emamectin benzoate 5% SG (440 g/ha). To broaden the regional context of the study, the findings were compared with author-provided 2025 local benchmark data that evaluated eco-friendly biorationals and conventional standalone chemistry (quinalphos 25EC) under similar regional agro-climatic conditions. Over the four-year evaluation cycle, the T2 module consistently outperformed the farmer's practice, restricting mean pod damage to 4.62%–8.31% compared with 7.23%–14.62% in T1. This pest suppression translated into grain yield increases of 8.50% to 11.83% over T1. During the 2024 season, characterised by severe regional abiotic stress that reduced base yields by more than 50%, the T2 module maintained higher net returns (Rs. 4,515/ha) than the control plots (Rs. 2,279/ha). In comparison, the standalone applications of quinalphos 25EC and Neem Seed Extract (NSE 5%) reported in the author-provided 2025 local benchmark dataset achieved grain yields of 8.80 q/ha and 8.60 q/ha, respectively. While standalone chemical treatments such as quinalphos recorded an Incremental Benefit-Cost Ratio (ICBR) of 1:9.61 due to lower initial application costs, the field-scale T2 rotation module achieved economic safety margins with a peak ICBR of 11.68 and total B:C ratios up to 2.48. Furthermore, although conventional broad-spectrum chemicals may disrupt beneficial fauna, incorporating targeted biorationals such as NSE 5% and Bacillus thuringiensis can help maintain populations of natural enemies, including ladybird beetles and spiders, and may support the integration of chemical rotations with biological conservation. This study indicates that a multi-mechanism insecticidal rotation can provide an effective and remunerative option for stabilising pulse production under variable rainfed production systems.