Ministry of Agriculture and Lands
Grape Root Rot and Decline
Phytophthora and Pythium Root Rots
(Phytophthora spp., Pythium ultimum)
Root diseases caused by Phytophthora or Pythium spp. have not been common in the Okanagan/Similkameen in recent years. These diseases are typically sporadic, usually occurring on single vines that are excessively irrigated. Affected vines are smaller than nearby healthy plants and the foliage may become chlorotic or colour prematurely. A canker develops near the soil line and usually extends downward to the roots. Removal of the periderm exposes the necrotic woody tissue underneath. Roots may become blackened and decayed; and smaller fibrous roots may die. Death of the vines may occur within 2 years from the time symptoms appear.
Roesleria Root Rot
A root rot caused by the fungus Roesleria subterranea has also occurred sporadically in Okanagan vineyards. It is considered to be a weak root pathogen that colonizes injured or dead roots, from where it may also invade healthy roots. During a 2007/08 survey of grapevine decline problems, roesleria root rot was found in several vineyards in vines that were also infected with Cylindrocarpon.
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| Fruiting bodies of Roesleria subterranea growing on a
grape root. Photo courtesy Michael Weis, Agriculture & Agri-Food Canada |
Control
Cultural:
Prevent root rots with good water management and by providing drainage if needed. Phytophthora and Pythium are “water molds” which are favoured by very wet conditions.
In replant sites, remove as many old roots as possible before replanting vineyards.
Chemical:
There are no fungicides registered for control of these soil-borne diseases on grape in Canada.
December, 2008
