Plant Disease (2013) 97, 86-92

H.A. Olson, S.N. Jeffers, K.L. Ivors, K.C. Steddom, J.L. Williams-Woodward, M.T. Mmbaga, D.M. Benson and C.X. Hong (2013)
Diversity and mefenoxam sensitivity of Phytophthora spp. associated with the ornamental horticulture industry in the southeastern United States
Plant Disease 97 (1), 86-92
Abstract: Phytophthora isolates associated with ornamental plants or recovered from irrigation water in six states in the southeastern United States (Georgia, North Carolina, South Carolina, Tennessee, Texas, and Virginia) were identified and screened for sensitivity to mefenoxam. Isolates from forest and suburban streams in Georgia and Virginia were included for comparison. A new in vitro assay, utilizing 48-well tissue culture plates, was used to screen for mefenoxam sensitivity; this assay allowed high throughput of isolates and used less material than the traditional petri plate assay. In total, 1,483 Phytophthora isolates were evaluated, and 27 species were identified with Phytophthora nicotianae, P. hydropathica, and P. gonapodyides, the most abundant species associated with plants, irrigation water, and streams, respectively. Only 6% of isolates associated with plants and 9% from irrigation water were insensitive to mefenoxam at 100 μg a.i./ml. Approximately 78% of insensitive isolates associated with plants were P. nicotianae, and most of these (67%) came from herbaceous annual plants. Most of the insensitive isolates recovered from irrigation water were P. gonapodyides, P. hydropathica, P. megasperma, and P. pini, and 83% of the insensitive isolates from streams were P. gonapodyides. Overall, this study suggests that mefenoxam should continue to be a valuable tool in the management of Phytophthora diseases affecting ornamental plants in the southeastern United States.
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Link to article at publishers website
Database assignments for author(s): Heather Olson, Margaret T. Mmbaga, Steven N. Jeffers, Chuan-Xue Hong, D. Michael Benson

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Phytophthora megasperma		U.S.A. (SE)
	Phytophthora gonapodyides		U.S.A. (SE)
	Phytophthora nicotianae		U.S.A. (SE)
	Phytophthora hydropathica		U.S.A. (SE)
	Phytophthora pini		U.S.A. (SE)