- Author: Lynn Wunderlich
10), many growers are out pruning their vineyards. But with more rain coming, those pruning wounds will be susceptible to a host of canker disease pathogens, notably, Eutypa, Botryosphaeria and Esca disease. Wood canker diseases (a.k.a. "trunk" disease, because these pathogens can make it all the way to the trunk, killing the vine) are a huge issue in the decline and shortened lifespan of vineyards.
Richard Smart has likened the scourge of canker disease, found in nearly every vineyard, akin to the days of phylloxera before we understood how to manage it with rootstocks. So, what can a grower do to prevent canker disease?
#1 Prune as late as possible. I understand labor issues make this complicated. So, if you need to get some pruning done now:
#2Double prune your vines. "Double" pruning means using 2 passes to get the job done: the first pass, done earlier, leaves at least a foot of cane above the fruiting buds. The second pass, done as late as possible (up to or even past budbreak), finished the job down to a one or two bud spur, as appropriate for the cane. Double pruning will help prevent frost injury, delay budbreak (the most terminal buds will break first), and help prevent canker infection because the initial pruning wound will take the brunt of the injury, only to be removed for the final
#3 Treat pruning wounds prior to rain with a protectant. Several fungicides, including an organic option, are now registered for pruning wound protection-most are labelled for airblast application (long gone are the days of "painting" protectants on). Sprayers can be modified, the fan turned down or off, or a flat fan nozzle on a modified bar at wire height can be mounted. See the UCIPM guidelines here for a list of protectants.
#4. Burn or remove from the vineyard the diseased prunings.