Botryosphaeria: Botryosphaeria canker (or often called Bot canker) is the leading cause of grapevine cordon and trunk death in CA and many other grape growing regions.  Botryosphaeria spores can infect vines through pruning wounds, then cankers form near old pruning wounds and move down following the vascular system. A cross-section of an infected vine reveals brown discoloration of vascular tissues, and advanced symptoms often form a darkened wedge shape inside the woody tissue. Therefore, Bot canker is often indistinguishable from Eutypa dieback when only a cross-section of the infected trunk is examined. However, Eutypa dieback tends to show stunting of shoots and leaves, while Bot canker may cause water stress-type symptoms on green tissues.

Bot canker symptoms generally show up on spurs, cordons, and trunks of vines 10 years or older, leading to a slow decline of productivity and eventually resulting in vine loss.  However, young vines, which are also susceptible to Bot cancer infection, can experience a rapid decline of an infected vine. Botryosphaeria may also cause Marcophoma rot on grape berries, which is especially common with Muscadine grapes.

(Photo credit: left and right top: Mizuho Nita, right bottom: Renaud Travadon)

Causal Agents: Several Botryosphaeria spp. (B. australis, B. dothidea, B. lutea, B. obtusa, B. parva, B. rhodina, B. stevensii, and other associated species), cause cankers in older grapevines worldwide, and may lead to major losses in vineyard productivity.

Management: Prevention at the time of winter pruning is the best approach for management. Double pruning, protection of pruning wounds using paint with boron (trade name: B-Lock), and chemical control, such as use of thiophanate-methyl (trade name: Topsin-M) and/or myclobutanil (trade name: Rally) to protect pruning wounds, are known to reduce the risk of infection to pruning wounds.

Also, it is advised to prune vines on a day followed by several days of sunny conditions.  (I.e., avoid pruning before the rain) If you decide to use the aforementioned fungicides, make sure to refer to the label for the specific uses.  Although symptoms appear in the vineyard after 5-10 years of planting, young vines are as susceptible as the old vines; therefore, it is advised to implement a management plan from the early years of the vineyard.

For infected unproductive vines, remove the infected trunk or cordon arm 12 inches below the canker and move the infected wood out of the vineyard for burying or burning. Vine health is extremely important for the recovery after major cordon or trunk pruning. Provide sufficient water and nutrients to encourage healthy vegetative growth.

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