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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #289481
Title: Efficacy of management tools for control of Pythium root rot of Douglas fir seedlings, 2010

Author
item Grunwald, Niklaus - Nik
item Press, Caroline
item Rolfe, Kenneth - Kenny
item Weiland, Gerald - Jerry
item Davis, Elizabeth

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/2013
Publication Date: 3/11/2013
Citation: Grunwald, N.J., Press, C.M., Rolfe, K.J., Weiland, G.E., Davis, E.A. 2013. Efficacy of management tools for control of Pythium root rot of Douglas fir seedlings, 2010. Plant Disease Management Reports. 7:OT010.

Interpretive Summary: This study investigated the efficacy of fungicides and biopesticides for control of Pythium root rot of Douglas fir seedlings. This effort was conducted as part of the IR-4 Ornamental Horticulture program to evaluate fungicides and biopesticides for management of root, crown and stem rot of ornamental plants caused by Pythium species. Specific Pythium species used in this study were P. vipa, P. dissotocum, and P. irregulare. Controlled experiments were conducted to assess efficacy by treatment with fungicide or biopesticie and evlatuion of the seedlings that emerged. Certain treatments provided a significant stand improvement over non-treated controls. Fungicide treatments with Alude, Subdue, and Aliette were the best treatments, with Alude resulting in significant disease control for all Pythium species. Some treatments appeared to be somewhat specific for certain Pythium species. No toxicity to plants was observed for any treatment.

Technical Abstract: This study investigated the efficacy of management tools for control of Pythium root rot of Douglas fir seedlings. This effort was conducted as part of the IR-4 Ornamental Horticulture program to evaluate fungicides and biopesticides for management of root, crown and stem rot of ornamental plants caused by Pythium species. Specific Pythium species used in this study were P. vipa, P. dissotocum, and P. irregulare. Controls received only noninfested vermiculite. Pots were arranged in a randomized complete block design with 8 replications. All treatments (except biopesticides) consisted of fungicide drenches with the soilless mix/inoculum mixture. Soil mix for the biopesticide treatments was drenched with the chemical, left to air-dry for 3 days, mixed with Pythium isolates, moistened, and left to sit for 2 days before seeding. Seedling germination and stand counts were taken to assess effectiveness of treatments. Certain treatments provided a significant stand improvement over non-treated controls. Alude, Subdue, and Aliette were the best treatments, with Alude resulting in significant disease control for all Pythium species. To a lesser extent, Adorn, Heritage, BW240, BW240+Al, Disarm and Cg100 all had some impact on stand improvement varying somewhat by Pythium isolate used. While these treatments may have been significantly different from the unsprayed control, the stand was still markedly reduced in some cases less than 20% of seedlings emerged. Some treatments appeared to be somewhat specific for certain Pythium isolates. For example, Adorn performed similar to the chemical standards in the test against P. vipa but performed poorly against P. dissotocum and P. irregulare. No phytoxicity was observed for any treatment.