Over the past few years, a fungal disease that affects mostly young grape vines up to eight years old has been taking a costly toll in some of California’s coastal areas. Diseased plants must be removed, requiring significant replanting expenses.

Called Black Foot Disease or Young Vine Decline, it’s caused by infection with Cylindrocarpon spp. and Campylocarpon spp. fungal pathogens. Typically, vines, which appear to be growing normally for several seasons, suddenly stop growing. Usually, the vines stop pushing buds in the spring or shoots become very stunted and soon die back, reports Mark Battany, University of California Cooperative Extension viticulture advisor for San Luis Obispo and Santa Barbara Counties, in a recent article on his Grape Notes blog.

As described on the UC Davis Plant Pathology website, leaves of vines infected with Black Foot Disease appear to be scorched by water stress, and the entire vine becomes stunted, and frequently dies. In cross section, the disease is characterized by black streaking in the vascular tissue. Roots of infected vines have  black, sunken, necrotic lesions.

Typically, most of the roots look normal. They are well spread but very often shallow, developing parallel to the ground. Sometimes, a second root system develops close to the surface and this will feed the young plant for a while. Commonly, the diseased plants are J-rooted.

The largest losses from this disease have been in vineyards planted on ground that was recently farmed with intensive row crops, such as vegetables and flowers, and which were planted with 101-14 rootstock, Battany notes.

“The intensive cultivation of row crops may lead to high levels of the pathogens in the soil,” he says. “This will be exacerbated if the vines are subjected to wet and poorly drained conditions such as can occur if the soil is not adequately tilled to remove any plow pans and hard pans that may have formed from the previous cultivation.”

Rootstocks differ in their susceptibility to infection with these pathogens, he adds. Research by the Gubler Lab at UC Davis indicates that AXR1 has a high relative resistance, while 140R and 039-16 were the most susceptible of the rootstocks studied. This earlier testing did not include the 101-14 rootstock which has been commonly used in recent plantings in the coastal areas.

Limited field observations at the same site under identical conditions found 101-14 suffered loss rates of more than 50 percent. Meanwhile, losses of adjacent vines on 1103P were negligible, Battany notes

He offers these recommendations for planting vineyards on sites that have previously been farmed with row crops or sites with conditions that may otherwise favor Black Foot Disease:

Battany’s article, including photos of infected vines and a vineyard, is available at http://ucanr.edu/blogs/GrapeNotesBlog/

More details about the disease are available at http://plantpathology.ucdavis.edu/faculty/Gubler_W_Douglas/Gubler_Lab/Blackfoot_disease_of_grapevines/