Abstract
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.
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Claims 8
Claim · model-written summary
In vitro, P. irregulare isolates were approximately three times less sensitive to mefenoxam (0.20 μg/ml) than P. sylvaticum and P. ultimum (0.06 μg/ml each).
- Taxon
- P. irregulareGlobisporangium irregularee0
- Treatment
- mefenoxame0
- Interactor
- P. irregulareGlobisporangium irregularee0pathogen
- Second interactor
- P. sylvaticumGlobisporangium sylvaticume0pathogen
- Outcome
- sensitivee0
- Direction
- less sensitivee0
- Value
- 0.20 μg/mle0
- Comparator
- P. sylvaticume0
Verbatim
e0“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)”
Claim · model-written summary
Two mefenoxam-resistant isolates of P. ultimum were identified (≥311 μg/ml).
- Taxon
- P. ultimumGlobisporangium ultimume0
- Interactor
- P. ultimumGlobisporangium ultimume0pathogen
- Outcome
- resistant isolatese0
- Value
- ≥311 μg/mle0
Verbatim
e0“two resistant isolates of P. ultimum were identified (≥311 μg/ml)”
Claim · model-written summary
All three Pythium species were similarly sensitive to fosetyl-Al (1,256 to 1,508 μg/ml).
.jpg?width=60){kind=small}
PythiumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“All three Pythium spp. were similarly sensitive to fosetyl-Al (1,256 to 1,508 μg/ml)”
Claim · model-written summary
No fosetyl-Al-resistant isolates were found among the Pythium isolates.
- Outcome
- no resistant isolatese0
Not reportedTaxonInteractor
Verbatim
e0“no resistant isolates were found”
Claim · model-written summary
Fosetyl-Al consistently provided good protection against damping-off caused by Pythium species in Douglas-fir seedlings in the greenhouse.
- Taxon
- Douglas-fir
Pseudotsuga menziesiie2 - Treatment
- fosetyl-Ale0
- Interactor
- P. dissotocumPythium dissotocume0pathogen
- Second interactor
- P. irregulareGlobisporangium irregularee0pathogen
- Outcome
- protection against damping-offe0
- Direction
- good protectione0
- Qualifier
- P. 'vipa'e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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'”
e2“Douglas-fir (Pseudotsuga menziesii) seedlings inoculated with Pythium dissotocum, P. irregulare, and P. 'vipa'”
Claim · model-written summary
Phosphorous acid consistently provided good protection against damping-off caused by Pythium species in Douglas-fir seedlings in the greenhouse.
- Taxon
- Douglas-firPseudotsuga menziesiie2
- Treatment
- phosphorous acide0
- Interactor
- P. dissotocumPythium dissotocume0pathogen
- Second interactor
- P. irregulareGlobisporangium irregularee0pathogen
- Outcome
- protection against damping-offe0
- Direction
- good protectione0
- Qualifier
- P. 'vipa'e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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'”
e2“Douglas-fir (Pseudotsuga menziesii) seedlings inoculated with Pythium dissotocum, P. irregulare, and P. 'vipa'”
Claim · model-written summary
Other treatments, including mefenoxam, gave good or intermediate protection against damping-off, with efficacy depending on the Pythium species.
- Taxon
- Douglas-firPseudotsuga menziesiie2
- Treatment
- mefenoxame0
- Outcome
- protectione0
- Direction
- good or intermediate protectione0
- Qualifier
- efficacy depended upon which Pythium sp. was usede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Other treatments, including mefenoxam, also provided good or intermediate protection but efficacy depended upon which Pythium sp. was used”
e2“Douglas-fir (Pseudotsuga menziesii) seedlings inoculated with Pythium dissotocum, P. irregulare, and P. 'vipa'”
Claim · model-written summary
Growers should consider rotating mefenoxam with other fungicide chemistries or biological treatments to prevent further development and spread of mefenoxam-resistant isolates.
Not reportedTaxon
Verbatim
e0“Growers should consider rotating mefenoxam use with other fungicide chemistries or biological treatments to prevent further development and spread of mefenoxam-resistant isolates”