Abstract: The mixed virulence of abamectin B₂ and fluopyram was tested against second-instar juveniles of Meloidogyne incognita using the immersion method, and then the field control efficacy of two kinds of self-made nematocidal biochar-based functional fertilizers on tobacco root-knot nematode(Meloidogyne spp.) disease was studied by using the hole application method. The results showed that the compound combination of abamectin B₂ and fluopyram at a mass ratio of 4∶1 for their active ingredients exhibited the most significant synergistic effect, and their LC₅₀ (Lethal concentration 50) at 24, 48, 72 h post-treatment against second-instar juveniles of Meloidogyne incognita was 4.69, 1.77, 1.04 μg/mL, respectively, and the cotoxicity coefficients were 134.78, 127.77 and 146.31 correspondingly. When the nematocidal biochar-based functional fertilizers were applied at 60 g per plant in tobacco field, the field control efficacy of self-made 0.33% abamectin B₂ nematocidal biochar-based functional fertilizer(A) and 0.33% abamectin B₂-fluopyram (4∶1)nematocidal biochar-based functional fertilizer (B) against root-knot nematode disease were 47.36% and 63.30% at the peak stage of disease (Mid-roasting stage), and the efficacy of the complex formulation was significantly higher than that of the single formulation. The field control efficacy of the above two kinds of nematocidal biochar-based functional fertilizers were 67.65% and 67.59% at the end of flue-curing, respectively, and there was no significant difference between the two fertilizers.

Key words: tobacco root-knot nematode(Meloidogyne spp.) disease, abamectin B₂, fluopyram, nematocidal biochar-based functional fertilizer, field control effeciacy