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Ministry of Agriculture

Grape Diseases

Botryosphaeria Canker
(Botryosphaeria parva and B. dothidea)

A survey of grape decline problems in Okanagan vineyards was conducted in 2007/08 by Agriculture and Agri-Food Canada (O'Gorman, Haag & Sholberg). Botryosphaeria canker (also known as bot canker and black dead arm) was detected in vines ranging from 3-11 years of age in several vineyards. Two species of Botrytosphaeria were identified, including B. parva and B. dothidea. The vineyards where B. parva was isolated showed severe decline problems. This disease had not been previously diagnosed in grapevine from British Columbia.

Bot canker is known to occur in most viticulture regions of the world. In California, recent research has shown that over 9 species of Botryosphaeria can infect grapevines, and that the disease is very prevalent in that state. The following information is based on information from California and other viticultural areas.

Symptoms

Botryosphaeria produces black streaks in the xylem of infected wood, typically causing wedge-shaped cankers in the trunk and cordons. The cankers are most easily seen when the vine is cut in cross section. Black pycnidia (fungal fruiting bodies) form on diseased vine parts under the bark of cordons, trunks, and spurs. Other diseases, including Eutypa canker cause very similar symptoms. Eutypa has not yet been identified in B.C. vineyards.

In California, botryosphaeria canker causes death of arms, cordons and vines, often so suddenly that there are no foliar symptoms. It is commonly seen in vines 10 or more years old. In other areas, foliar symptoms such as chlorosis and stunting are more common. Symptoms may vary depending on the species of Botryosphaeria present. Typically diseased vines fail to break dormancy or suddenly wilt during the following growing season.

Vine decline caused by Botryosphaeria canker.  Photo courtesy Agriculture and Agri-Food Canada Internal discolouration of Botrytosphaeria-infected vines. Photo courtesy Agriculture and Agri-Food Canada

Disease Cycle

The fungus overwinters as pycnidia on diseased wood. Pycnidia release conidia (spores) when wet by rain or irrigation. Conidia are spread by water splash and wind to cause new infections, primarily  through fresh pruning wounds. Moisture is needed for infection, along with temperatures above 5 ° C.

Botryosphaeria can also infect other tree species, and could also be present in adjacent orchards, forests and riparian areas. The importance of spread from other host species to vineyards is not well understood.

Disease Prevention and Management

  • Remove visible cankers and dead or declining arms, cordons and vines.
  • Burn prunings from infected vines, or remove them from the vineyard.
  • Prune healthy-looking vines before sick vines. Disinfect pruning tools periodically, particularly after pruning vines with symptoms.
  • In California, late pruning during March results in less infection of pruning wounds. Optimal timing may be different in our climate. In general, warmer temperatures accelerate healing of pruning wounds, so wounds are susceptible for a shorter time. Pruning during a period of forecast dry weather would also help to reduce infection.
  • Good cultural practices help to maintain vigour and reduce losses.
  • There are no fungicide treatments for Botryosphaeria canker available in Canada.

Resources

January, 2009

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