The effects of CropGuard® on the motility, ultrastructure, and respiration of two Meloidogyne species
Keywords: furfural, oxygen consumption rate, respiration, root-knot nematodes, second-stage juvenile motility
AbstractThe progressive withdrawal of Class I nematicides from world markets necessitates investigation and exploitation of more environmentally friendly products with nematicidal or nematostatic properties. Scientific, baseline knowledge about the biology, ultrastructure, and physiology of Meloidogyne spp. pertaining to the mode of action of CropGuard®, with furfural as the active ingredient, is lacking. The product was evaluated over time (1, 24, 48, 72, and 96 hr) for its effects on M. incognita and M. javanica second-stage juveniles (J2) motility, ultrastructure, and specific oxygen consumption rate. Four CropGuard® concentrations (0.01, 0.1, 1, and 10%) and a tap water control were used for all experiments. All four product concentrations significantly inhibited the movement of J2 of both Meloidogyne spp. Scanning electronmicroscopy (SEM) results indicated that the cuticle surfaces of J2 suspended in the CropGuard® concentrations were not visibly damaged, but that their lateral line structures showed a “sunken” appearance. Specific oxygen consumption rate (O2) measurements confirmed that the respiratory physiology and motility of the J2 were adversely affected by the nematicide. Partial respiratory recuperation of M. incognita J2 occurred when they were transferred to sterile tap water after being suspended in the lower (0.01 and 0.1%) CropGuard® concentrations.