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Field evaluation of weather-based spray programs for the control of downy mildew of lettuce (Lactuaca sativa), caused by Bremia lactucae, in Quebec and Ontario

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dc.contributor.author Hovius, M.H.Y.
dc.contributor.author McDonald, M.R.
dc.contributor.author Carisse, O.
dc.contributor.author Philion, V.
dc.date.accessioned 2019-10-28T13:22:41Z
dc.date.available 2019-10-28T13:22:41Z
dc.date.copyright 2007
dc.date.created 2007
dc.date.issued 2007
dc.identifier.other https://doi.org/10.1080/07060660709507432
dc.identifier.uri http://hdl.handle.net/10214/17521
dc.description.abstract Each year, downy mildew caused by Bremia lactucae occurs in lettuce-producing regions of Quebec and Ontario. Trials were conducted to determine if the disease could be managed with fewer fungicide applications, using disease forecasting. Disease-forecasting programs designed to time the application of fungicide sprays were evaluated for control of downy mildew of lettuce in 1997 and 1998 at 9 field sites. Disease forecasting was based on lesion development following a recorded sporulation-infection period (SIP), with leaf wetness between 3:00 AM and 10:00 AM and temperature between 5 and 20 °C. Presymptom sprays with the protectant fungicide mancozeb were applied before lesions were expected; they were based on 110 accumulated degree-days following a SIP, but not within 7 days of a previous spray. Post-latent-period sprays with the systemic fungicide metalaxyl-M in combination with mancozeb were applied after forecasted lesion development; they were based on 135 accumulated degree-days, but not within 14 days of a previous spray. The effects of forecasted sprays were compared with those of weekly applications of mancozeb and with those of metalaxyl-M or metalaxyl applied in furrow at the time of seeding or transplanting. Downy mildew developed at 7 of the 9 sites. The number of SIPs recorded at all sites ranged from 7 to 17. In 8 of the 9 sites, there were fewer mancozeb applications with the presymptom program than with the weekly sprays, that is a reduction of one, two, and three sprays at six, one, and one sites, respectively. This resulted in a 16%–60% reduction in applied fungicide. When metalaxyl-M plus mancozeb was applied according to the post-latent-period forecast, one or two sprays were required, that is a reduction of two, three, and four applications at four, three, and two sites, respectively, compared with the weekly application of mancozeb alone. Metalaxyl-M or metalaxyl applied in furrow provided control for 30–40 days after seeding or transplanting. The number of fungicide applications can be reduced with acceptable disease control if a forecasting program is followed. en_US
dc.language.iso en en_US
dc.publisher Taylor & Francis for the Canadian Phytopathological Society en_US
dc.subject disease forecasting en_US
dc.subject disease management en_US
dc.subject metalaxyl-M en_US
dc.subject lettuce en_US
dc.subject downy mildew en_US
dc.subject Bremia lactucae en_US
dc.title Field evaluation of weather-based spray programs for the control of downy mildew of lettuce (Lactuaca sativa), caused by Bremia lactucae, in Quebec and Ontario en_US
dc.type Article en_US
dc.rights.license All items in the Atrium are protected by copyright with all rights reserved unless otherwise indicated.
dcterms.relation M.H.Y. Hovius, M.R. McDonald, O. Carisse & V. Philion (2007) Field evaluation of weather-based spray programs for the control of downy mildew of lettuce (Lactuca sativa), caused by Bremia lactucae, in Quebec and Ontario, Canadian Journal of Plant Pathology, 29:1, 9-17, DOI: 10.1080/07060660709507432


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