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Citeable URL: http://ir.library.oregonstate.edu/concern/articles/9s161778b

To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the American Phytopathological Society and is in the public domain. The published article can be found at:  http://apsjournals.apsnet.org/loi/pdis.

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Attribute Name	Values
Creator	Grünwald, Niklaus J. Weiland, Jerry E. Santamaria, Luisa
Abstract or Summary	Mefenoxam and fosetyl-Al are common fungicides used to supplement disease control of Pythium damping-off and root rot in forest nurseries of the western United States. However, it is unknown whether fungicide-resistant Pythium isolates are present or whether new fungicide and biological treatments might also provide supplemental disease control. Isolates of Pythium irregulare, P. sylvaticum, and P. ultimum from three forest nurseries were evaluated for in vitro sensitivity to mefenoxam and fosetyl-Al. A greenhouse study was also conducted to assess efficacy of fungicide and biological treatments in Douglas-fir (Pseudotsuga menziesii) seedlings inoculated with Pythium dissotocum, P. irregulare, and P. ‘vipa’. P. irregulare was approximately three times less sensitive to mefenoxam (0.20 μg/ml) than P. sylvaticum (0.06 μg/ml) and P. ultimum (0.06 μg/ml), and two resistant isolates of P. ultimum were identified (≥311 μg/ml). All three Pythium spp. were similarly sensitive to fosetyl-Al (1,256 to 1,508 μg/ml) and no resistant isolates were found. In the disease control efficacy trial, both fosetyl-Al and phosphorous acid consistently provided good protection against damping-off caused by P. dissotocum, P. irregulare, and P. ‘vipa’. Other treatments, including mefenoxam, also provided good or intermediate protection but efficacy depended upon which Pythium sp. was used. Growers should consider rotating mefenoxam use with other fungicide chemistries or biological treatments to prevent further development and spread of mefenoxam-resistant isolates.
Resource Type	Article
DOI	10.1094/PDIS-09-13-0998-RE
Date Available	2014-07-28T20:07:33+00:00
Date Issued	2014-07
Citation	Weiland, J. E., Santamaria, L., & Grünwald, N. J. (2014). Sensitivity of Pythium irregulare, P. sylvaticum, and P. ultimum from forest nurseries to mefenoxam and fosetyl-Al, and control of Pythium damping-off with fungicide and biological treatments. Plant Disease, 98(7), 937-942. doi:10.1094/PDIS-09-13-0998-RE
Series	Plant Disease Vol. 98 no. 7
Rights Statement	Copyright Not Evaluated
Funding Statement (additional comments about funding)	Funding for this research was provided by USDA CRIS 303-5358-12220-003-00D, the Pacific Area Wide Pest Management Program for Methyl Bromide Alternatives, and The IR-4 Project.
Publisher	American Phytopathological Society
Peer Reviewed	Yes
Language	English [eng]
Replaces	http://hdl.handle.net/1957/50833
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