Differential Response of Meloidogyne enterolobii, M. floridensis, M. haplanaria, and M. incognita to sub-lethal doses of non-fumigant nematicides

Authors: POUDEL, NABIN - University Of Georgia; Davis, Richard; SEVERNS, PAUL - University Of Georgia; MCAVOY, THEODORE - University Of Georgia; JAGDALE, GANPATI - University Of Georgia; BRENNEMAN, TIMOTHY - University Of Georgia; CHOWDHURY, INTIAZ - University Of Georgia

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2025
Publication Date: 5/7/2025
Citation: Poudel, N., Davis, R.F., Severns, P.M., Mcavoy, T., Jagdale, G.B., Brenneman, T.B., Chowdhury, I.A. 2025. Differential Response of Meloidogyne enterolobii, M. floridensis, M. haplanaria, and M. incognita to sub-lethal doses of non-fumigant nematicides. Phytopathology. 115:1215-1222. https://doi.org/10.1094/PHYTO-01-25-0028-R.
DOI: https://doi.org/10.1094/PHYTO-01-25-0028-R

Interpretive Summary: Root-knot nematodes (RKN; Meloidogyne spp.) are among the most widespread and damaging plant-parasitic nematodes. Although M. incognita is the most prevalent RKN species, other aggressive species such as M. enterolobii, M. floridensis, and M. haplanaria have recently been detected in multiple Georgia, USA vegetable fields. Farmers use chemical nematicides to manage M. incognita populations because most vegetable crops do not yet have effective host resistance against it. We evaluated the effects of sublethal doses of the non-fumigant nematicides Salibro (fluazaindolizine), Nimitz (fluensulfone), Velum Prime (fluopyram), and Vydate (oxamyl) on motility, egg hatching, and reproduction of these four RKN species. In vitro behavioral response assays revealed significant variation in motility among species, with M. enterolobii being the least sensitive to all evaluated nematicides. Population growth in greenhouse conditions indicated that M. enterolobii reproduction was affected less by nematicides than any of the other evaluated Meloidogyne species. While most nematicides displayed strong ovicidal activity, Salibro appeared to have poor ovicidal efficacy for all RKNs. No differences were observed among Meloidogyne species in their egg hatching responses to nematicides. In this study, we conducted the first comprehensive evaluation of these nematicides on motility, reproduction, and egg hatching in these RKN species. Our results indicated that M. enterolobii is likely to be more difficult to control due to its tolerance of the chemical nematicides and may become a more impactful crop pest as it spreads in the absence of effective soil fumigants.

Technical Abstract: Root-knot nematodes (RKN; Meloidogyne spp.) are among the most widespread and damaging plant-parasitic nematodes. While M. incognita is the most prevalent RKN species, the aggressive species M. enterolobii, M. floridensis, and M. haplanaria have recently been detected in multiple Georgia, USA vegetable fields. Producers use chemical nematicides to manage M. incognita populations because most vegetable crops do not yet have effective host resistance against it. We evaluated the effects of sublethal doses of the non-fumigant nematicides fluazaindolizine, fluensulfone, fluopyram, and oxamyl on motility, egg hatching, and reproduction of these four RKN species. In vitro behavioral response assays revealed significant variation in motility among species, with M. enterolobii being the least sensitive to all evaluated nematicides. Population growth in greenhouse conditions indicated that M. enterolobii reproduction was affected less by nematicides than any of the other evaluated Meloidogyne species. While most nematicides displayed strong ovicidal activity, fluazaindolizine appeared to have poor ovicidal efficacy for all RKNs. No differences were observed among Meloidogyne species in their egg hatching responses to nematicides. In this study, we conducted the first comprehensive evaluation of these nematicides on motility, reproduction, and egg hatching in these RKN species. Our results indicated that M. enterolobii is likely to be more difficult to control due to its tolerance of the chemical nematicides and may become a more impactful crop pest as it spreads in the absence of effective soil fumigants.