Biological attributes of Salibro™, a novel sulfonamide nematicide. Part 1: Impact on the fitness of Meloidogyne incognita, M. hapla and Acrobeloides buetschlii

Abstract

Summary Salibro™ is a novel sulfonamide nematicide containing the active substance (a.s.) fluazaindolizine (Reklemel™ active). Its biochemical mode of action is presently unknown but in internal laboratory studies it exerted adverse effects on various fitness parameters (motility, mobility and infectivity) of two species of root-knot nematodes (Meloidogyne incognita and M. hapla). While not causing an immediate knock-down effect on second-stage juveniles (J2) during the first 24-48 h of exposure to concentrations of 1-50 ppm (a.s.), exposed J2 showed clearly visible symptoms of toxicological effects (including characteristic body postures) and started to lose both their mobility as well as infectivity. This decrease in mobility and infectivity was nonreversible, even if the J2 were washed, and was already observed after pre-exposure periods of 24-48 h at 1-50 ppm (a.s.). Lower temperatures during the exposure period (4-10°C) did not prevent toxicological effects of treated J2 but slightly delayed the time-to-effect. By contrast, various vermiform life-stages of the bacteriophagous nematode, Acrobeles buetschlii, did not show any signs of intoxication or reduced motility during continuous exposure to Salibro™ at up to 250 ppm (a.s.). Salibro™ slightly increased hatching of M. hapla but did not significantly impact the hatching of M. incognita at concentrations up to 50 ppm (a.s.). No adverse effects on hatching were observed for A. buetschlii at concentrations up to 250 ppm (a.s.). The results indicate that Salibro™ is an effective and selective nematicide and will be a useful new tool in sustainable nematode management.