Deposition, dissipation, and minimum effective dosage of the fungicide carbendazim in the pepper‐field ecosystem

BACKGROUND In order to reduce application dosage of carbendazim (CBD), the effects of different droplet sizes and application rate on initial deposition, retention rate, and field control efficacy of CBD in the pepper plant (Capsicum annuum L.) were studied under laboratory and field conditions. RESULTS Based on eight types of nozzles at six concentrations of 646.8, 582.2, 517.5, 414.0, 310.5, and 258.7 g a.i./hm2, the initial deposition amount of CBD in the pepper plant showed a first increased and then decreased trend with the increasing application dosages. The initial deposition amount of CBD in the pepper leaves and stems was highest when using the nozzle ST110‐03 at 200 μm volume median diameter (VMD) and 350 L/hm2 application rate. HPLC‐MS/MS analysis revealed that CBD was first converted to 2‐aminobenzimidazole, which then transformed into benzimidazole and 2‐hydroxybenzimidazole by deamination and hydroxylation, and ultimately mineralized to carbon dioxide and water via the cleavage of the imidazole ring in pepper plant. The dissipation rate of CBD was fruits > roots/stems > leaves > soils. After 7 days of application, the field efficacy of CBD at six concentrations on pepper anthracnose (Colletotrichum spp.) were 94.1%, 91.3%, 82.3%, 76.5%, 47.0%, and 41.2%, respectively. CONCLUSION The results revealed the deposition and dissipation characteristics of CBD, and the minimum effective dosage on pepper anthracnose decreased to 80% of the minimum recommended dose in the open field pepper ecosystem. The study will contribute to the CBD reduction by improving its utilization rate in the pepper‐field ecosystem. © 2019 Society of Chemical Industry Key findings: Minimum effective dosage of carbendazim (CBD) was revealed based on the interrelation among application dosage, deposition amount in target zone, and field control efficacy on pepper anthracnose in pepper ecosystem.