Management of mustard aphid with exogenous application of salicylic acid in Nagaon district of Assam

Abstract

Mustard aphid, Lipaphis erysimi (Kaltenbach), is one of the most destructive insect pests of rapeseed–mustard,
causing substantial yield losses under field conditions. A field experiment was conducted during three consecutive rabi
seasons (2023–24, 2024–25 and 2025–26) at the Zonal Research Station, Shillongani, Assam Agricultural University, to
evaluate the efficacy of exogenous application of salicylic acid against mustard aphid and its effect on coccinellid
predators, seed yield and economics. The experiment was laid out in a randomized block design with five treatments
comprising salicylic acid at 0.5 mM (69 ppm), 1.0 mM (138 ppm) and 1.5 mM (207 ppm), thiamethoxam 25 WG @ 0.1 g
L-¹ and an untreated control. The pooled results revealed that salicylic acid at 1.5 mM was the most effective treatment,
recording the lowest aphid population of 14.09, 17.96, 15.30 and 5.93 aphids plant-¹ at 3, 7, 10 and 14 days after spray
(DAS), respectively. The treatment resulted in the highest reduction over control (56.59%) and produced the maximum
seed yield (1509.44 kg ha-¹), which was statistically at par with thiamethoxam 25 WG @ 0.1 g L-¹ 25 WG @ 0.1 g L-¹ (1503.89
kg ha-¹). Economic analysis indicated that salicylic acid at 1.5 mM generated the highest net return (Rs. 64,087.28 ha-¹)
and benefit-cost ratio (2.17). The treatment also supported a higher population of coccinellid predators during both
flowering (2.40 predator’s plant-¹) and siliqua formation stages (3.27 predators plant-¹) compared with thiamethoxam 25
WG @ 0.1 g L-¹. The findings suggest that foliar application of salicylic acid at 1.5 mM effectively suppresses mustard
aphid infestation, enhances yield and profitability, and conserves natural enemies, making it a promising eco-friendly
alternative for sustainable mustard aphid management.