Compatibility of fluazaindolizine and oxamyl with Pasteuria penetrans on spore attachment to juveniles of Meloidogyne javanica and M. incognita.

Fluazaindolizine is a novel sulfonamide nematicide that is the active ingredient (a.i.) of Salibro™, a.i. Reklemel™. Its compatibility with Pasteuria penetrans, a bacterial parasite of root-knot nematodes (Meloidogyne spp.), was investigated in populations of M. javanica and M. incognita. Spores of a single P. penetrans isolate (Pp 3) or a blend of six isolates were incubated in the suspensions of fluazaindolizine (SalibroTM 500SC, at 5, 50, and 250 ppm a.i.) and oxamyl (Vydate™ 10 L, 10% (a.i.) at 25 and 50 ppm a.i.) for 1, 7, and 21 days; controls were incubated in water. Thereafter, the suspensions were washed through a cellulose filter (3 µm) so as to remove the nematicide, and the spores retained on the filter were suspended in water. Juveniles (J2) were exposed in these spore suspensions in Petri dishes and the number of attached spores was recorded. Neither fluazaindolizine nor oxamyl, at all the tested dosages, had any negative effect on the rate of spore attachment. The spore encumbered J2 from some experiments were used to infect tomatoes. Females without egg masses were extracted from the roots after 50 days and checked for eggs in ovaries and mature spores of P. penetrans. Despite no mature spores present in the females, there was evidence of a low percentage of infection in a few treatments. A possible explanation is that since the bacterium had been kept stored in the form of dried roots for a long period, its ability to infect nematodes was decreased.Fluazaindolizine is a novel sulfonamide nematicide that is the active ingredient (a.i.) of Salibro™, a.i. Reklemel™. Its compatibility with Pasteuria penetrans, a bacterial parasite of root-knot nematodes (Meloidogyne spp.), was investigated in populations of M. javanica and M. incognita. Spores of a single P. penetrans isolate (Pp 3) or a blend of six isolates were incubated in the suspensions of fluazaindolizine (SalibroTM 500SC, at 5, 50, and 250 ppm a.i.) and oxamyl (Vydate™ 10 L, 10% (a.i.) at 25 and 50 ppm a.i.) for 1, 7, and 21 days; controls were incubated in water. Thereafter, the suspensions were washed through a cellulose filter (3 µm) so as to remove the nematicide, and the spores retained on the filter were suspended in water. Juveniles (J2) were exposed in these spore suspensions in Petri dishes and the number of attached spores was recorded. Neither fluazaindolizine nor oxamyl, at all the tested dosages, had any negative effect on the rate of spore attachment. The spore encumbered J2 from some experiments were used to infect tomatoes. Females without egg masses were extracted from the roots after 50 days and checked for eggs in ovaries and mature spores of P. penetrans. Despite no mature spores present in the females, there was evidence of a low percentage of infection in a few treatments. A possible explanation is that since the bacterium had been kept stored in the form of dried roots for a long period, its ability to infect nematodes was decreased.

The discovery of fluazaindolizine: A new product for the control of plant parasitic nematodes.

Fluazaindolizine is a new highly effective and selective product for the control of plant parasitic nematodes. Specificity for nematodes coupled with absence of activity against the target sites of commercial nematicides suggests that fluazaindolizine has a novel mode of action. The discovery, structure-activity development and biological properties for this new class of nematicides are presented.

The impact of fluazaindolizine on free-living nematodes and the nematode community structure in a root-knot nematode infested vegetable production system.

BACKGROUND: Fluazaindolizine is a novel sulfonamide nematicide that is currently under commercialization in various countries. Four trials (two in tomato, two in zucchini) were carried out over two growing seasons in a root-knot nematode (RKN; Meloidogyne incognita)-infested plastic house to test the effects of a single application of fluazaindolizine at 1000 and 2000 g ha-1 , on RKN, the resident nematode community and to estimate any side effects on the soil food web and soil ecological functions. The composition of the nematode community was evaluated at three sampling times, pre-treatment (before soil preparation), at planting (after nematicide application) and at harvest. Nematode abundance and nematode-based ecological indices, such as maturity indices, soil food web indices (Structure, Basal, Enrichment index) and metabolic footprints were calculated and compared between the untreated and nematicide treatments at various sampling times. RESULTS: In both crops the test rates of fluazaindolizine significantly reduced both the soil numbers of RKN as well as the observed root galling at harvest. Fluazaindolizine treatments showed a low impact on the numbers of other plant-parasitic nematodes, and at harvest the numbers of some ectoparasites as Telotylenchus even showed higher values within the nematicide-treated plots than in the untreated control. Overall, fluazaindolizine treatments neither decreased the bacterivorous, fungivorous or omnivorous nematode densities, nor reduced the maturity and soil food web indices. However, we observed some slight reductions in the structure index as well as increases in the basal index that might indicate some adverse impact on soil functions resulting from the nematicide application. Still those impacts were considered small compared to the impact of the soil preparation. CONCLUSIONS: Overall, fluazaindolizine showed a good level of selectivity towards RKN and therefore could become a useful tool within integrated nematode management approaches that also complements soil health and maintaining diversity in soil.

Effects of pyrrolizidine alkaloids on the performance of plant-parasitic and free-living nematodes.

BACKGROUND: Chemical nematicides such as methyl bromide have for decades played a significant role in the management of plant-parasitic nematodes. Their application is problematic because of negative environmental impacts, and therefore methyl bromide was phased out in Europe in 2005. A possible alternative to synthetically derived nematicides is seen in the use of plants and/or their secondary metabolites. These plants could either be used as nematicidal green manure or as a source for nematicidal extracts. This study aimed to evaluate the effects of 1,2-dehydropyrrolizidine alkaloids (PAs), a group of secondary plant metabolites found in hundreds of plant species throughout the world, on the performance of plant-parasitic and free-living nematodes. RESULTS: PAs induced nematicidal, ovicidal and repellent effects on different plant-parasitic and free-living nematodes. There was no conclusive ranking in toxicity for the different structural types of PAs tested. However, the effects were often more pronounced for the tertiary than for the oxidised form of PAs. Further, large differences were observed in the susceptibility of different nematode species to PAs. CONCLUSIONS: PAs do affect several performance parameters and developmental stages of nematodes. Therefore, PA-producing plants such as species of Crotalaria, Ageratum or Senecio might be promising candidates for nematode management strategies. [Correction made here after initial online publication].