American Potato Journal

, Volume 62, Issue 10, pp 499–510 | Cite as

Controlling potato late blight with systemic-protectant fungicide combinations of metalaxyl and mancozeb

  • H. W. Platt


Disease development was monitored weekly in field plots inoculated withPhytophthora infestans and treated with metalaxyl, mancozeb or metalaxyl/ mancozeb combinations. Late blight pressure was moderate to severe in 1981 and 1983 and was slight to moderate in 1982 and 1984. In 1982–84 all treated plots had significantly less foliar damage and late blight tuber rot than untreated plots. Use of metalaxyl alone resulted in the greatest increase in disease (up to 80% defoliation) in the latter part of the growing season. Under slight to moderate disease pressure, metalaxyl/mancozeb and mancozeb treatments provided significantly better disease control than metalaxyl. Under moderate to severe disease pressure, high levels of disease (65% defoliation) occurred by the end of the season with mancozeb and metalzxyl/mancozeb on 7- and 14-day spray schedules, respectively. However, significantly better control (about 20% defoliation) was obtained during early season, rapidly developing epidemic conditions when only three applications of metalaxyl/mancozeb were included in a 7-day mancozeb spray program.

Key words

Phytophthora infestans Solanum tuberosum acylaline fungicides 


El desarrollo de la enfermedad fue seguido semanalmente en el campo, en parcelas inoculadas conPhytophthora infestans, y tratadas con metalaxyl, mancozeb, o combinaciones de metalaxyl y mancozeb. La intensidad del tizón tardío, fue moderada a severa en 1981 y 1983, y leve a moderada en 1982 y 1984. En 1982–84, todas las parcelas tratadas tuvieron daños foliares y pudrición de tubérculos significativamente menores que las parcelas no tratadas. El uso de metalaxyl solo presentó el mayor incremento de la enfermedad (por encima de 80% de defoliación) al final de la estación de cultivo. Bajo una intensidad de leve a moderada de la enfermedad, los tratamientos con metalaxyl/mancozeb, y mancozeb, permitieron un control significativamente mejor de la enfermedad que el tratamiento con metalaxyl. Bajo una intensidad moderada a severa de la enfermedad, ocurrieron altos niveles (65% de defoliación) de la misma, los que se presentaron al final de la estación de cultivo, para mancozeb, y metalaxyl/mancozeb, en programas de aspersión de 7 y 14 días, respectivamente. Sin embargo, un control significativamente mejor (alrededor de 20% de defoliación) durante el inicio de la estación de cultivo, desarrolló rápidamente en una epidemia cuando se incluyeron solamente tres aplicaciones de metalaxyl/mancozeb en un programa de aspersión de 7 días, con mancozeb.


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Copyright information

© Springer 1985

Authors and Affiliations

  • H. W. Platt
    • 1
  1. 1.Research StationAgriculture CanadaCharlottetown

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