Responses of nematodes to nematicidal applications following extended exposures to subnematicidal stress

Abstract

Long-terme exposures of plant-parasitic nematodes, Xiphinelna index, Meloidogyne incognita, and Pratylenchus vulnus to subnematicidal stresses of carbofuran, oxamyl and phenamiphos can alter their responses to subsequent nematicidal treatments. Responses Vary not only with the different nematicide used but with the different nematode species. Subnematicidal stressing with carbofuran and phenamiphos reduced reproductive potential in X. index, while phenamiphos stressing reduced reproductive potential in M. imognita. However, carbofuran stressing appeared to increase, reproductive potential in P. vulnus. Cross-susceptibility was observed in carbofuran and oxamyl stressing, which made X. indexmore susceptible to phenamiphos, while carbofuran stressing increased the susceptibility of P. vu2nzks to oxarnyl. Long-term subnematicidal stressing of al1 three nematodes with the three nematicides appeared to induce resistance and cross-resistance phenomena in the form of indifference and increased populations in response to nematicidal treatments. In some cases the behavioral response took the form of an apparent habituation. Soi1 leachings from carbofuran and phenamiphos stock cultures of X. index provided protection from corresponding nematicidal treatments, while addition of leachings from oxamyl and phenamiphos cultures of M. incognita assisted in decreasing populations following the respective nematicidal applications. The addition of oxarnyl leachings also contributed in decreasing X. index population levels. &SUME Réaction des nématodes lors de traitements neinaticides consécutifs à une exposition à des doses sublétales de nénzaticides