Effects of neonicotinoid insecticides against grape phylloxera on vineyard soil microbial communities.

Soil microbiomes play a pivotal role in ecosystem functioning and agricultural productivity. Although insecticides effectively control grape phylloxera, their impact on vineyard soil microbial communities remains poorly understood. Here, we used amplicon sequencing to assess the responses of bacterial and fungal communities to the insecticides thiamethoxam, clothianidin, and dinotefuran. The results revealed significant compositional shifts after insecticide application, particularly in soils treated with dinotefuran. Beta diversity analysis revealed significant structural separation of bacterial communities among insecticide treatments (P < 0.05), whereas fungal communities showed no such differences (P > 0.05). Several beneficial microbes involved in nutrient cycling and plant health (including Nitrososphaera, Planctomyces, Paenibacillus, Chitinophaga, and Clonostachys) were significantly reduced after dinotefuran and clothianidin treatments. The cyanobacterium Phormidium was more abundant in control soils. Conversely, after insecticide treatment, the relative abundance increased for numerous pathogenic fungi (Fusarium, Cylindrocladium, Cladosporium, Acrocalymma, Phaeosphaeria, Exserohilum, and multiple Cyphellophora species) may elevate the risk of disease outbreaks. Soils treated with dinotefuran were enriched in microorganisms potentially associated with pollutant degradation (e.g., Rhodoplanes, Sporosarcina, Arthrobacter, and Mycobacterium). Interestingly, the relatively high abundances of beneficial taxa involved in nutrient cycling and disease suppression were maintained after thiamethoxam and clothianidin treatments, and the entomopathogenic fungus Lecanicillium increased in clothianidin-treated soils. Tax4Fun2 functional prediction indicated higher bacterial membrane transport activity in control soils. In contrast, FUNGuild functional prediction revealed that insecticide-treated soils had increased abundances of pathotrophic and saprotrophic fungi, which may further elevate vineyard disease risk. Overall, these findings clarify the differential impacts of insecticides on vineyard soil microbial communities, highlight the importance of selecting insecticides that will maintain vineyard sustainability, and provide guidance for designing integrated pest management (IPM) strategies that balance grape phylloxera control with microbiome conservation.