Field Efficacy of Fluopyram Suspension Concentrate against Pine Wilt Disease and Its Distribution and Persistence in Pine Tree Tissues

Fluopyram is a novel nematicide compound with systemic activity, and it is a potential chemical agent for controlling pine wilt disease, which is devastating pine trees worldwide. Here, a fluopyram suspension concentrate (SC) was used to determine its efficacy in controlling pine wilt disease, its distribution in pine tree tissues, and its environmental degradation. Fluopyram SC had an evident inhibitory effect on Pestalotiopsis sp. and showed a good preventive effect on pine wilt disease in healthy pine seedlings. In the field application, after spraying onto the canopy of pine trees, fluopyram was absorbed and translocated downward to all parts of the tree via the branches and needles, and its distribution was stable at 30 days post-application (all samples’ mean residual concentration = 1.166 mg/kg). In addition, the maximum concentration of fluopyram residue in soil and water was 1.139 and 0.099 mg/kg, respectively, at 30 days post-application when fluopyram was significantly degraded. The control efficiency of fluopyram SC in the forest reached 90.48% when the formulation was sprayed by agricultural unmanned aerial vehicles. The half-life of fluopyram SC was 346.6 days, with a persistence of 3 years. These results indicate that spraying fluopyram SC could effectively reduce the number of pine trees dying from pine wilt disease.