Botryosphaeria Dieback

Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback make up a complex of "trunk diseases" caused by different wood-infecting fungi. Botryosphaeria dieback (commonly known in California as "Bot canker") causes death of spurs, arms, cordons, canes, and sometimes the upper section of the trunk, depending on the location of the wood canker. Wedge-shaped (sometimes circular to oblong) wood cankers form in infected wood and are indistinguishable from those associated with Eutypa and Phomopsis dieback. Unlike Eutypa dieback, no characteristic foliar symptoms are associated with Botryosphaeria dieback. Instead, the leaves on a shoot originating from an infected spur or cane will wilt and the shoot will die back completely during the growing season. Other symptoms of Botryosphaeria dieback include dead spurs, stunted shoots, and bud mortality. Such symptoms are shared in common among multiple trunk diseases, which often occur in mixed infection within the vineyard and even within an individual vine.

Botryosphaeria dieback is the most common and widespread trunk disease in California and some of the causal species (e.g., Neofusicoccum parvum) are among the most aggressive trunk pathogens. Symptoms first become apparent in vineyards 5 to 7 or more years old, but the infections actually occur in younger vines. Pycnidia, the overwintering structures that produce spores, are embedded in diseased woody parts of vines. During winter rainfall, spores are released and wounds made by winter pruning provide infection sites. Wine, table, and raisin-grape cultivars are susceptible to disease. Under California conditions, pruning as late as possible in the dormant period has been shown to be very effective in reducing the risk of infection. Delayed pruning takes advantage of reduced susceptibility of pruning wounds to infection and avoids the period of highest spore release during winter rain events. After a pruning wound is infected, the pathogen establishes a permanent, localized wood infection, which cannot be eradicated by fungicide applications.

See EUTYPA DIEBACK for management practices.

• Guide to Vineyard Trunk Diseases in California (PDF) (If printing, use this version and in print settings under size options choose "actual size" and "auto portrait/landscape orientation")