Determining the Tolerance of Native Trichoderma Species to Fungicides Used in Control of Soilborne Fungal Diseases

Systemic fungicides are frequently used to manage soilborne diseases in vegetables but there application represents an environmental risk and negatively affects biological control agents such as Trichoderma. This research evaluated how several common fungicides including azoxystrobin+metalaxyl-M+fludioxonil (A+M+F), fludioxonil+metalaxyl-M (F+M), propamocarb hydrochloride+cymoxanil (P+C), captan (C), copper oxychloride (CO), and tolclofos-methyl (T) impact native Trichoderma species. Our results showed that Tolclofos-methyl inhibited mycelial growth of all Trichoderma species, showing a 63.5-68.7% reduction. It also severely hindered conidia germination (62.2-77.7%). Fludioxonil+metalaxyl-M was another strong inhibitor of conidia germination (64.4-77.7%). The azoxystrobin+metalaxyl-M+fludioxonil and captan also severely limited the conidia germination of T. harzianum Tr124, T. afroharzianum (Tr132 and Tr138), T. virens (Tvr2 and Tvr3). Copper oxychloride showed the least effect in inhibiting mycelial growth of native Trichoderma isolates (1.0-12.3%) and conidia germination (8.9-17.7%). In conclusion, this study demonstrated that fungicides commonly used in Türkiye to combat damping-off and root rot in vegetables can affect the Trichoderma population in agricultural areas. Future studies should focus on monitoring the population dynamics of biocontrol agents of insecticides and herbicides applied to soil in vegetable production.