Biological attributes of Salibro™, a novel sulfonamide nematicide. Part 3: biocompatibility with beneficial soil fungi

Abstract

Summary Over the last few years, novel synthetic nematicides, such as Salibro™ nematicide (a.s. fluazaindolizine - Reklemel™ active), Velum Prime® (a.s. fluopyram) or Nimitz® (a.s. fluensulfone), have been commercialised in various regions around the world. Whilst considerable scientific information exists on their field efficacy against plant-parasitic nematodes, very little has been published on their bio-compatibility with beneficial soil fungi. In this paper in vitro studies are presented with various nematophagous (Athrobotrys, Monacrosporium, Harposporium, Purpureocillium), entomoparasitic (Beauveria, Isaria) and disease-suppressive (Trichoderma) fungi that were exposed to these nematicides under laboratory conditions. Assessments were made on their impact on radial growth and sporulation of those fungi. Clear differences in sensitivity to the nematicides were seen between the different fungi. Intrinsically, fluopyram showed the strongest adverse effects on the tested fungi that often became already visible at a concentration of 5 ppm (a.s.). Negative effects were significant at higher concentrations of 50 ppm. Fluensulfone showed limited adverse impacts on the tested fungi at 5 ppm (a.s.) but clearly inhibited most of the fungi at 50 ppm (a.s.). Fluazaindolizine had the least impact of the novel nematicides, with no adverse effects recorded on any species at 5 ppm (a.s.), and very minor growth reductions at 50 ppm (a.s.). Even when tested at 250 ppm (a.s.) fluazaindolizine still showed no impact on Purpureocillium lilacinum, as well as only a weak impact on some Trichoderma species. Vydate (a.s. oxamyl), which was often included as a traditional carbamate nematicide in the test, also showed excellent bio-compatibility with the tested fungi at concentrations of from 5 to 50 ppm (a.s.). Overall, the studies showed that beneficial soil fungi differ in their intrinsic sensitivity to these modern nematicides. These interactions may be considered when designing integrated nematode management programmes that leverage endemic or introduced biocontrol agents. However, it should be noted that additional studies under field conditions with recommended label rates of the products are needed to confirm the trends seen in these laboratory data.