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American Potato Journal

, Volume 61, Issue 2, pp 83–92 | Cite as

Metalaxyl and other fungicides for control ofPhytophthora infestans on potato in northwest Washington State

  • Gene D. Easton
  • Michael E. Nagle
Article

Abstract

In northwest Washington State, fungicidal control of late blight caused byPhytophthora infestons was evaluated for three years. During 1977, a high rainfall year with supplemental sprinkler irrigations, all metalaxyl and chlorothalonil treatments reduced tuber rot at harvest, but only metalaxyl extended control of tuber rot after 4 months’ storage. During 1978, a high rainfall year, one application of metalaxyl sprayed over or dusted on potato seed pieces at planting or applied five times to foliage at 2 or 4 wk intervals gave excellent blight control equal to that with chlorothalonil applied to foliage every 2 wk.

In 1979, a low rainfall year,P. infestons did not kill plants in untreated plots until October. Five applications of metalaxyl sprayed every 2 wk on foliage did not control foliage blight. However, metalaxyl reduced foliage blight when dusted on cut potato seed pieces. Mancozeb sprayed every 2 wk also gave excellent control. The possibility that metalaxyl applied to foliage is effective in late blight control only when washed into the soil by rainfall or irrigation for uptake by roots is discussed.

Yields and percent U.S. No. 1 grade tubers were not significantly affected by any treatment in these 3-year trials.

Key Words

Late blight mancozeb chlorothalonil 

Resumen

En el Estado de Washington en el noroeste de los EE.UU., se evaluó durante tres años el control por fungicidas del tizón tardio causado porPhytophthora infestons. Durante 1977, un año con un alto nivel de precipitaciones y con riego suplementario por aspersión, todos los tratamientos de metalaxil y clorotalonil redujeron la pudrición del tubérculo al momento de la cosecha. Pero sólo el metalaxil prolongó su control de la pudrición del tubérculo hasta después de 4 meses de almacenamiento.

Durante 1978, un año con un alto nivel de precipitaciones, una aplicación de matalaxil rociado o espolvoreado sobre los tubérculos-semillas en la siembra o aplicado cinco veces en el follaje a intervalos de 2 a 4 semanas, dio un excelente control del tizón tardío, igual que el control por clorotalonil aplicado al follaje cada 2 semanas.

En 1979, un año con un nivel bajo de precipitaciones,P. infestans no causó la muerte de las plantas en parcelas sin tratar hasta octubre. Cinco aplicaciones del metalaxil rociado en el follaje cada dos semanas no controlaron el tizón tardío. Sin embargo, el metalaxil redujo el tizón en el follaje al ser espolvoreado sobre los tubérculos-semillas cortados. El Mancoceb rociado cada dos semanas también dio un excelente control. Se discute la posibilidad de que el metalaxil aplicado en el follaje sea efectivo en el control del tizón tardio sólo al penetrar en el suelo con el agua de la lluvia o del riego y así ser asimilado por las raices.

Los rendimientos y el porcentaje del primer tamaño según escala estadounidense no resultaron significativamente afectados por ningún tratamiento en los ensayos de esos tres años.

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Copyright information

© 1984 1984

Authors and Affiliations

  • Gene D. Easton
    • 1
  • Michael E. Nagle
    • 1
  1. 1.Department of Plant PathologyWashington State University, Irrigated Agriculture Research and Extension CenterProsser

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