Discovery and Mechanism of 1,4-Dichloropyrido[3,4-d]pyridazine as a Potential Nematicidal Candidate

Plant nematode disease management is still a difficult problem in agricultural production. To develop novel green nematicides, pyridazine compounds with nematicidal activities against Ditylenchus destructor (D. destructor), Bursaphelenchus xylophilus (B. xylophilus), Aphelenchoides besseyi (A. besseyi), and Meloidogyne incognita (M. incognita) were discovered. The LC₅₀ values of compound C2 were 7.1 and 3.4 mg/L against D. destructor and A. besseyi, respectively. Compound C2 not only caused an adverse oxidative stress response of nematodes, resulting in intestinal damage, but also significantly inhibited egg hatching of D. destructor. Compound C2 may lead to decreased cellular tolerance and antioxidant function of D. destructor by significantly downregulating the differential gene of the heat shock 70 kDa protein, thereby accelerating the cell litter process and ultimately leading to the death of the nematode. Compound C2 can serve as a potential novel nematicide worthy of further study in the future.