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

Abstract

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.

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

“…Many field studies have demonstrated the efficacy of fluazaindolizine against RKN on a series of crops including carrots, cucumber, tomato, and squash ( Becker et al ., 2019 ; Desaeger and Watson, 2019 ; Hajihassani et al ., 2019 ; Talavera et al ., 2021 ; Zhang et al ., 2021 ). However, to our knowledge, the efficacy of fluazaindolizine against RKN on sweet potato had not been previously investigated.…”

“…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 ).…”

“…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 ). However, little is known about the field performance of fluazaindolizine against SRKN on sweet potato, so it was investigated in this study.…”

Sensitivity of Meloidogyne enterolobii and M. incognita to fluorinated nematicides

“…13 Although synthetic non-fumigant nematicides have shown considerable efficacy in glasshouse and field trials, [20][21][22][23][24] not all plantparasitic nematodes share the same level of sensitivity to these compounds. 20,[25][26][27] For instance, in vitro exposure to fluazaindolizine for 72 h was more lethal to M. incognita and Tylenchulus semipenetrans (Cobb) than to Pratylenchus brachyurus (Godfrey) or Heterodera schachtii (Schmidt). 28 In vitro incubation studies with fluensulfone have shown similar results, with Aphelenchoides besseyi (Christie), A. fragariae (Ritzema Bos), Bursaphelenchus xylophilus (Steiner and Buhrer) and Ditylenchus dipsaci (Kühn) showing tolerance to fluensulfone exposure, whereas Pratylenchus penetrans (Cobb) and Xiphinema index (Thorne) were immobilized by this compound.…”

“…oxamyl), having greater specificity to targeted organisms as well as reduced risk to environmental and human health. 13 Although synthetic non-fumigant nematicides have shown considerable efficacy in glasshouse and field trials, [20][21][22][23][24] not all plantparasitic nematodes share the same level of sensitivity to these compounds. 20,[25][26][27] For instance, in vitro exposure to fluazaindolizine for 72 h was more lethal to M. incognita and Tylenchulus semipenetrans (Cobb) than to Pratylenchus brachyurus (Godfrey) or Heterodera schachtii (Schmidt).…”