Screening of chemical attractants for second-stage juveniles of meloidogyne species on agar plates

The attractiveness of 60 aromatic compounds, mainly carboxylic acids, alcohols, aldehydes, and phenols, to second-stage juveniles (J2) of four Meloidogyne species (M. hapla, M. incognita, M. javanica, and M. marylandi) was evaluated based on the relative density of J2 attracted to a test compound on an agar plate in an 8.5-cm Petri dish. Three types of nematode responses were observed in the single-compound assays: attraction, in which J2 were attracted to test compounds; concentration-dependent attraction, in which J2 were attracted to the zone located 1-2 cm from test compounds; and no response. None of the test compounds effectively attracted M. incognita or repelled J2 of any species. Thirty-five compounds attracted J2 of at least one of the other three nematode species. Highly effective attractants were trans-cinnamic acid, salicylic acid, 4 '-hydroxy-3 '-methoxyacetophenone, o-vanillin, carvacrol, 3-methoxybenzyl alcohol, 2-methoxycinnamaldehyde, trans-p-methoxycinnamaldehyde, 4-methoxy-3-methylbenzaldehyde, 2-methoxy-4-propenylphenol, and thymol. Salicylic acid dissolved in the agar reduced the attraction of M. marylandi J2 to salicylic acid and to o-vanillin. Two- and three-compound assays revealed differences in attractiveness to M. marylandi J2 between or among structural isomers of the attractants. o-Vanillin and salicylic acid were much more attractive to M. marylandi than vanillin and the two isomers of salicylic acid, respectively. It is not clear whether nematodes utilize the attractants found in the study for locating hosts in nature, but the attractants may have potential for use in nematode control.

Automated summary

The study evaluated the attractiveness of 60 aromatic compounds to second-stage juveniles of four Meloidogyne species, with salicylic acid and other compounds being highly effective attractants. Differences in attractiveness were observed between structural isomers of the attractants.