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.

Root‐knot nematode damage to a cucurbit double crop is increased by chloropicrin fumigation on the previous tomato crop

“…These products are known to be much more selective than fumigants, and therefore less likely to negatively impact overall soil biology. 6,14,[56][57][58][59][60] In the case of fluensulfone, in five out of 10 trials root-knot nematode damage on the double crop was reduced following fluensulfone application on the first crop. It is not clear why only fluensulfone and none of the other non-fumigant nematicides reduced root-knot nematode damage on the second crop, but possibly fluensulfone was more effective at reducing nematode reproduction on the first crop, which has been observed in previous field experiments.…”

Meloidogyne incognita Management Using Fumigant and Non-fumigant Nematicides on Sweet Potato

“…Fluazaindolizine, oxamyl, and fluopyram all negatively impacted free-living nematodes, but only in 1 of 3 yr of the study (2020). A lab study showed that sensitivity to fluazaindolizine differed by free-living nematode species and the fitness of some species of bacteria-feeding species were negatively impacted ( Talavera et al ., 2021 ), but in general, free-living nematode fitness were not adversely impacted ( Thoden and Wiles, 2019 ; Talavera et al ., 2021 ). Our results are generally in line with these findings, and greater sensitivity of free-living nematodes to fluazaindolizine in 2020 could be a result of a greater proportion of bacterivores at the site in 2020, since this trophic group is more sensitive to fluazaindolizine ( Talavera et al ., 2021 ).…”

“…Fluazaindolizine is a novel sulfonamide nematicide ( Lahm et al ., 2017 ). The mode of action remains unknown, but lab studies showed that it has adverse effect on RKN motility and infectivity ( Thoden and Wiles, 2019 ; Watson, 2021 ). Several field studies on various crops including tomato, carrot, and squash have shown the potential of fluazaindolizine as a new nematicide against RKN ( Becker et al ., 2019 ; Desaeger and Watson, 2019 ; Talavera et al ., 2021 ; Zhang et al ., 2021 ).…”