Induced resistance and nutrient deterrence reduce aphid reproduction and improve crop yield, phenolic defense, and economic benefits of canola (Brassica napus L.) in the field

Abstract

Cabbage aphid, Brevicoryne brassicae L., is a key pest of canola (Brassica napus L.), all over the world. A few studies have focused on its field management using inducers or nutrients; however, none of them focused on aphid reproduction indices, phenolic defense, and economic returns. Induced resistance treatments were comprised of 0, 0.5, and 1 mM concentrations of SA—Salicylic Acid and CA—Citric Acid, while nutrient deterrence had 25 and 50 kg ha⁻¹ doses of Si—Silicon and AS—Ammonium Sulfate. Both approaches were compared to an insecticide (Carbosulfan 20 EC) and untreated control for two years in a field experiment. Although insecticide was an effective treatment, its impacts were not long-lived. The 1 mM SA reduced aphid reproduction the most, followed by 0.5 mM SA, 1 mM CA, and 0.5 mM CA. Similarly, in nutrient deterrence, Si 50 kg reduced the aphid reproduction indices followed by Si 25 kg and AS 25 kg. Seed yield was improved by 37.8% in AS 50 kg, followed by Si 50 kg (29.8%), and 1 mM SA (25.4%), over the insecticide. Other treatments were not performing well. Phenolic defense chemicals were highest in Si 50 kg, followed by Si 25, AS 25 kg, and 1 mM SA. Marginal analysis followed by residual analysis revealed AS 25 kg ha⁻¹ to be the most economical treatment followed by 0.5 mM SA for recommending to the farming community. Conclusively, both approaches showed the potential to manage cabbage aphids on canola and improved crop yield and phenolic defense; however, additional research is desired to explore their possible mechanism of resistance in plants.