Abstract
The residual effect of the fungicide chlorothalonil on the vesicular-arbuscular mycorrhizal (VAM) symbiosis was evaluated in a greenhouse experiment. The soil used was an oxisol (Tropeptic Eutrustox) treated with P to obtain target levels near-optimal for VAM activity or sufficient for nonmycorrhizal host growth. In the uninoculated soil treated with the former P level, the fungicide reduced VAM colonization of roots and completely suppressed symbiotic effectiveness measured in terms of pinnule P content. When this soil was inoculated with Glomus aggregatum, symbiotic effectiveness was significantly reduced but not eliminated by 50 mg of the fungicide kg−1. At higher chlorothalonil levels, VAM effectiveness but not VAM colonization was completely suppressed in the inoculated soil. The pattern with which chlorothalonil influenced tissue P content and dry matter yield at the time of harvest closely paralleled its effect on VAM effectiveness. In the soil treated with P level sufficient for nonmycorrhizal host growth, the adverse effect of the fungicide on the above variables was appreciably milder than when the host relied on VAM fungi for its P supply. The toxic effect of the fungicide, therefore, was partly offset by P fertilization, suggesting that VAM fungi were more sensitive to chlorothalonil than the host. Our results demonstrate that although the toxic effect of chlorothalonil declined as a function of time, a significant level of toxicity persisted 12.5 weeks after the chemical was applied to soil.
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Contribution from Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3625.
Contribution from Hawaii Institute of Tropical Agriculture and Human Resources Journal Series No. 3625.
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Habte, M., Aziz, T. & Yuen, J.E. Residual toxicity of soil-applied chlorothalonil on mycorrhizal symbiosis in Leucaena leucocephala . Plant Soil 140, 263–268 (1992). https://doi.org/10.1007/BF00010603
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DOI: https://doi.org/10.1007/BF00010603