Effect of Quintozen, Benomyl and Carbendazim On the Interaction Between the Endomycorrhizal Fungus Glomus Fasciculatum and the Root-Knot Nematode Meloidugyne Incognita On Cotton

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The effect of Quintozen, Benomyl, and Carbendazim, applied as a drench, on the VA endomycorrhizal fungus Glomus fasciculatum, the root-knot nematode Meloidogyne incognita and on the interaction between the two was studied on cotton in the greenhouse. G. fasciculatum did not affect plant growth or nematode population density 30 days after simultaneous inoculation at planting, but caused significant increases in plant growth and a significant reduction in M. incognita population density and reproduction 50 days after inoculation. The fungicides did not alter nematode populations on nonmycorrhizal plants. Benomyl and Carbendazim, however, significantly reduced G. fasciculatum antagonistic activity toward M. incognita reproduction when applied at planting. The diminution of antagonism was stronger than the effect of the fungicides on symbiont root colonization of cotton. Carbendazim, which was less toxic to G. fasciculatum than Benomyl, did not influence mycorrhizal intensity when applied at planting or 25 days later. Nematode numbers increased significantly on mycorrhizal plants when Benomyl was applied at planting, but no significant change was noticed with similar applications of Carbendazim. Conversely, there were fewer nematodes in mycorrhizal plants when the fungicides were applied 25 days after planting. The results demonstrated that fungicide concentration and time of application are important factors influencing the antagonistic interaction between endomycorrhizal fungi and root-knot nematodes on cotton. Effective use of VA mycorrhizae in nematode control systems, therefore, will require proper screening of fungicides for fungicidal activity to endomycorrhizal fungi.