Control efficacy and joint toxicity of broflanilide mixed with commercial insecticides to an underground pest, the black cutworm in highland barley

Background: The highland barley, Hordeum vulgare L., is a staple food crop with superior nutritional functions in Xizang, China. It is often damaged by the black cutworm, Agrotis ipsilon (Hufnagel), which is an underground pest and difficult to effectively manage. To introduce a novel insecticide with unique mode of action, broflanilide (BFL) and its binary mixtures with chlorantraniliprole (CAP), fluxametamide, β-cypermethrin or imidacloprid were screened out as seed treatment to control black cutworm in highland barley in the present study.

Results: In the laboratory bioassays, BFL had outstanding insecticidal activity to black cutworm with a median lethal dose (LD₅₀) of 0.07 mg kg^-1. The mixture of BFL × CAP at the concentration ratio of 7:40 exhibited the highest synergistic effect with a co-toxicity coefficient of 280.48. In the greenhouse pot experiments, BFL and BFL × CAP seed treatments at 8 g a.i. kg^-1 seed could effectively control black cutworm, with a low percentage of injured seedlings <20% and high control efficacies of 93.33-100% during a period of 3-12 days after seed emergence. Moreover, BFL and BFL × CAP seed treatments could promote the seed germination and seedling growth of highland barley at the tested temperatures of 15, 20 and 25 °C.

Conclusion: Our results indicated that BFL and BFL × CAP were effective and promising insecticides as seed treatment to control black cutworm in highland barley. © 2024 Society of Chemical Industry.