While scientists debate the Latin name of this little fungus (depending on which plant it attacks and who you talk to), Eutypa dieback is no joke. Also known as dead arm disease, Cytosporina, and gummosis, you often won’t see symptoms in time to save the tree.
Symptoms of Eutypa dieback
In apricot trees, the leaves on an infected branch will wither and die but remain attached to the tree (flagging). Oozing cankers occur along lower limbs, and the bark turns darker. Two years after Eutypa dieback infection takes hold, grape vines display leaf cupping and distortion, chlorosis, and stunted new growth. A cross-section of the wood shows V-shaped cankers.
This insidious microorganism moves toward the trunk, killing the entire tree or vine. Also, the fungus responsible for Eutypa dieback seems to be broadening its dietary preferences to include almond, apple, blueberry, citrus, fig, kiwifruit, nectarine, olive, peach, pear, plum, and walnut, as well as Ceanothus spp., chokeberry, crab apple, oak, oleander, poplar, native California buckeye, big-leaf maple, and willow. Remove infected trees and vines immediately to avoid spreading to healthy plants.
Preventing Eutypa dieback
Like most fungi, moisture is necessary for their development. While most pruning occurs in winter, plants susceptible to Eutypa dieback are best pruned in summer. All pruning cuts are wounds. While trees and vines can develop a protective callus, these cuts need time to dry and heal. Never apply sealants to these wounds. Sealants hold moisture in, creating the perfect habitat for disease. If it rains 2-6 weeks after pruning, the Eutypa dieback fungus can take hold and kill your tree. Improperly aimed sprinklers can cause similar risks.
Eutypa dieback controls
If you discover an infected branch, you may be able to save the plant by removing infected limbs at least 12” below any internal symptoms. Examine the exposed cross-section for signs of infection. Dip your pruning tools in a household cleaner between each cut. Keep cutting down the branch until you reach healthy wood. Unfortunately, this method is only marginally successful.
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