Efficacy of Insecticides in Managing Fall Armyworm (Spodoptera frugiperda J.E. Smith) on Maize Crop Under Natural Field Condition

The fall armyworm (Spodoptera frugiperda J.E. Smith) is a polyphagous and voracious insect pest that causes significant damage to maize crops in Nepal. Nepalese farmers often resort to expensive insecticides to manage this pest, substantially increasing the cost of maize production. This study aimed to evaluate various insecticides to identify options that are cost-effective, readily available, and affordable for farmers. Insecticides with different modes of action were tested for their effectiveness in controlling fall armyworm larvae through foliar spray applications 15 days after sowing under natural field conditions at the National Maize Research Program, Chitwan, Nepal, during the winter seasons of 2022 and 2023. The study revealed that all treatments significantly reduced plant damage and increased grain yield compared to the untreated control (p < 0.005). Spinosad 45% EC at 0.3 ml/liter of water demonstrated the lowest foliar damage (4.5%), followed by flubendiamide 480 SC at 1 ml/3 liters of water (20.9%) and thiamethoxam 12.6% + lambda-cyhalothrin 9.5% ZC at 0.5 ml/liter of water (28.2%), compared to the untreated control (88.9%). Similarly, the highest grain yield (9.79 t/ha) was obtained with spinosad, followed by flubendiamide 480 SC (8.95 t/ha) and thiamethoxam 12.6% + lambda-cyhalothrin 9.5% ZC (8.46 t/ha), compared to the untreated control (1.76 t/ha). Lambda-cyhalothrin 5% EC at 2 ml/liter of water also performed well (7.5 t/ha). Although MP AP3 Grease at 0.15 grams/whorl and thiamethoxam 25% WG at 0.5 g/liter of water were the least effective among the treatments they were still significantly superior to the untreated control. A negative correlation was observed between the mean damage score, mean foliar damage percent and grain yield.