Impact of three novel nematicides on <i>Bursaphelenchus xylophilus</i> and pine wilt disease

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 EC (emulsifiable concentrate) and 15% JB-3 SC (suspension concentrate)], and INV-06 MS (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 four-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 pre-disease 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.