Diamide seed treatment may protect early soybean growth stages against Helicoverpa armigera

Abstract

In intensive soybean cropping systems, early-season pest insects such as lepidopteran larvae can seriously compromise crop establishment. Using a polyphagous global pest ̶̶ the Old World bollworm Helicoverpa armigera (Lepidoptera: Noctuidae), we determined the potential of seed treatments with diamide or neonicotinoid-carbamate mixture for systemic plant protection and residual efficacy against noctuid larvae. In controlled edaphoclimatic conditions, we infested differently aged soybean plants and recorded plant damage and insect mortality, growth, development, and fecundity to assess lethal and sublethal post-exposure effects. The seed treatments reduced plant damage by 50% during 1–7 days after plant emergence. The lowest damage (<25% defoliation) occurred on plants treated with chlorantraniliprole or cyantraniliprole. These diamides caused larval mortality >80% until 14 days after soybean emergence, which was the window of residual control efficacy. Carbofuran or thiodicarb + imidacloprid caused less than 50% larval mortality and minor plant protection against the larvae. There were sublethal effects on the growth, development, and fecundity of the insects surviving on plants of the insecticide seed treatments. The diamide seed treatments reduced the overall insect fitness for a longer time after plant emergence than did the other treatments. Therefore, soybean seed treatment with chlorantraniliprole or cyantraniliprole is potentially efficacious against noctuid larvae in the VE–V1 soybean growth stages (emergence until the first trifoliate), causing lethal and sublethal effects on the insects. Judicious use and effective resistance management for these systemic compounds are relevant as they are helpful for seed treatment and foliar applications against diverse targets.