(1) Pine wilt disease (PWD) is a devastating disease of pine forests caused by the pine wood nematode (PWN), Bursaphelenchus xylophilus. Control of the disease is a worldwide problem due to the impossibility of using chemical nematicides on a large scale and for long periods. (2) Based on preliminary tests of microemulsion quality and stability, the optimum formulation was selected from 14 formulated microemulsions. The median lethal concentration (LC₅₀) of the selected formulation at 48 h after treatment of B. xylophilus was 31.45 μg/mL of emamectin benzoate. The active ingredient reached the apical branches of Pinus thunbergii within 90 days of injection. (3) P. thunbergii was inoculated with B. xylophilus at 100 days post-injection, and the trees treated with the formulation remained uninfected for 450 days. Trunk injection exerted substantial control over PWD. (4) These results indicate that this formulation has the advantages of good transportability and long persistence in pine trees after injection and that it effectively prevents PWD. Therefore, this emamectin benzoate formulation can effectively reduce PWD occurrence in pine forests.

Injecting chemical agents into tree trunks is a key method for preventing pine wilt disease (PWD). However, the long-term use of conventional trunk injection agents such as emamectin benzoate (EB) and avermectin (AVM) may lead to nematode resistance. Therefore, it is crucial to evaluate the potential of new-generation nematicides, including fluopyram (FLU) and its compound formulations, as alternatives to EB and AVM in PWD prevention. In this study, four trunk injection agents, i.e., 5% FLU microemulsion (ME), 2% AVM + 6% FLU ME, 5% EB ME, and 5% AVM emulsifiable concentrate (EC), were injected into Pinus massoniana trunks, and their residual dynamics over time and preventive effects on PWD were compared. Results showed that all agents were transported to various parts of the trees within 90 days post-injection, with FLU showing significantly stronger translocation compared with EB and AVM. At 660 days post-injection, the active ingredient levels of 5% FLU ME in apical branches remained significantly higher than those of the other three agents at both tested doses (30 and 60 mL). Artificial inoculation with 10,000 Bursaphelenchus xylophilus nematodes per tree at 90 days post-injection showed that trees injected with 5% FLU ME and 2% AVM + 6% FLU ME had nearly 100% disease prevention rates at both doses, outperforming 5% EB ME and 5% AVM EC. A second nematode inoculation at 480 days post-injection showed that 2% AVM + 6% FLU ME showed 50% efficacy, outperforming 5% EB ME (25% efficacy). These findings offer a foundation for developing alternative trunk injection strategies for future PWD management in China.

Options for pesticide control of pine wilt disease (PWD) are currently limited, with efficacy also varying markedly. Thus, there remains an urgent need for stable, highly effective agents to improve field control measures. This study assessed the laboratory toxicity and field effectiveness of three novel nematicides against Bursaphelenchus xylophilus (Steiner & Buhrer 1934) Nickle 1981 (pine wood nematode [PWN]), examining their impact on nematode mortality, feeding, reproduction, and egg hatching at different temperatures, as well as their control efficacy against PWD in Pinus massoniana Lamb. saplings. The tested products included two novel amide nematicides, namely JB-3 (5% JB-3 emulsifiable concentrate and 15% JB-3 suspension concentrate [SC]) and INV-06 microcapsule suspension. All three nematicides were highly effective against PWN, with the JB-3 formulations exhibiting superior nematicidal activity and thermal stability relative to INV-06. However, INV-06 showed superior inhibition of PWN egg hatching and population growth. In disease-severity trials on 4-year-old P. massoniana plants, all three nematicides effectively controlled PWD, especially when applied early. Specifically, spray treatments with 15% JB-3 SC and INV-06 during predisease or early stages yielded pronounced therapeutic effects. In summary, laboratory toxicity assays and field efficacy tests on P. massoniana saplings confirmed that the nematicides effectively killed PWN and suppressed its reproduction, offering promising control for diseased pine trees.