Response of Soil Non-Target Microbes and Physicochemical Properties to Four Selected Chemical Fungicides in Fusarium Wilt-Affected Cashew Fields

Limited to possible toxicity, fungicides continue to be considered the effective method to control diseases including fusarium wilt. This current study presents the effect of carbendazim, azoxystrobin, thiophanate methyl, and propamocarb hydrochloride on soil microbes and physicochemical properties. Using the culture-dependent method studied from 2023 to 2024, soils from infested and treated in between 2023 and 2024 were analyzed from three different cashew fields. Findings revealed that the application of fungicides altered the microbial population and physicochemical properties across locations. High dosage (20 g/l) of fungicides had a toxicity effect on bacteria, fungi, and actinomycetes by inhibiting the growth by more than 50%. Field application of fungicide at the recommended dosage of 15 g/l displayed a non-toxic effect on the microbial population and physicochemical properties. Their application remarkably increased bacteria, fungi and actinomycetes, despite propamocarb hydrochloride and carbendazim respectively slightly reduced the population of fungi from 150.1 to 126.7×10<sup>6</sup> colony forming unit (CFU)/g and actinomycetes from 207.3 to 127.3×10<sup>6</sup> CFU/g. Again, fungicides increased organic matter, total nitrogen, phosphorus and potassium but decrease to accepted level of pH, electrical conductivity, and cation exchange capacity. Conclusively, the application of azoxystrobin, carbendazim, and thiophanate methyl and propamocarb hydrochloride at appropriate rate are recommended at farm level. Further monitoring on residual level for appropriate risk assessment of chemical fungicides is required.