Abstract
Foliar sprays of Difolatan were equal to or slightly better than those of maneb for the control of late blight when applied at equivalent rates of active ingredient. Difolatan foliar sprays, in general, resulted in less late blight tuber rot than did maneb sprays. Foliar sprays of Bordeaux mixture or Difolatan produced residues of these fungicides in the soil. These residues were greater in the surface soil (0 to 1/2 inch depth) than in the 1 to 2 inch layer, but were not sufficient to inhibit indirect germination of the sporangia ofP. infestans in soil leachates. Similar results were obtained with applications of Bordeux mixture or Difolatan to the soil in the absence of any foliar spray. Residues from foliar sprays of Difolatan plus soil treatments of Difolatan or Bordeaux mixture, made before and after the last cultivation, inhibited indirect germination ofP. infestans sporangia in soil leachates from the surface soil, but not from the 1 to 2 inch layer of soil. Application of foliar sprays of Bordeaux mixture to plots given soil treatments of Difolatan before the last cultivation resulted in fungitoxic residues in the surface soil and in the 1- to 2-inch layer of soil, but not when Difolatan soil treatments were made after the last cultivation. Similar results were obtained when maneb foliar sprays were applied to plots that had received soil applications of Difolatan.
Resumen
Aspersión de hojas con Difolatan era igual o aun mejor que la aspersión con maneb para el control de rancha o hielo fungoso cuando se habían aplicado a tasas equivalentes de ingradiente activo. Aspersiones de hojas con Difolatan resultaron, en general, en menos podredumbre de tubérculos causada por la rancha que las aspersiones con maneb. Aspersiones de hojas con mezvla de Bordeaux o con Difolatan dejaron resíduos de estos fungicidas en el suelo. De estos resíduos había más en la superficie del suelo (0 a 1/2 pulgada) que en el nivel de 1 a 2 pulgadas, pero no fueron suficientes para prevenir la germinación indirecta de esporangios deP. infestans en percolaciones de suelo. Resultados similares se obtuvieron aplicando la mezcla de Bordeaux o Difolatan al suelo sin aplicarlo a las hojas. Resíduos de espersiones de hojas con Difolatan, además de los del tratamiento del suelo con Difolatan o mezcla de Bordeaux, hecho antes y después del último cultivo, inhibieron la germinación indirecta de los esporangios deP. infestans en percolaciones de suelo obtenidas de la superficie pero no del nivel de la 1 a 2 pulgadas. Aplicación de la aspersión de hojas de mezcla de Bordeaux a lotes el suelo de los cuales había sido tratado con Difolatan antes del a última cultivación dejó resíduos fungitóxicos en la superficie del suelo y también en el nivel de 1 a 2 pulgadas, pero no hubo resíduos cuando tratamientos con Difolatan habían sido hechos después de la última cultivación. Resultados similares se obtuvieron cuando las aspersiones de hojas con maneb se aplicaron a lotes que habían tenido aplicaciones de Difolatan en el suelo.
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Cetas, R.C., Leach, S.S. Phytophthora infestans sporangial germination and tuber rot reduced by soil residues of fungicides. American Potato Journal 46, 174–181 (1969). https://doi.org/10.1007/BF02872360
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DOI: https://doi.org/10.1007/BF02872360