identification and confirmation—Pierce's disease
Pierce's disease is usually evident by the scorching and reddening of leaves. Symptoms of several other
disorders of grapes can be confused with Pierce's disease. Any disorder that weakens or causes deterioration
in vine growth in late summer or fall may lead to delayed or stunted growth the following spring. Eutypa
dieback symptoms in spring include stunted shoots and small, chlorotic, distorted leaves, which resemble
those of Pierce's disease. Pruning wound cankers, however, are not associated with Pierce's disease as
they are with Eutypa dieback. Phylloxera causes a decline of vines; look for phylloxera insects on roots.
Oak root fungus can cause wilting, along with discoloration and drying of fruit and foliage, but fungal
fans will be evident beneath bark in crown area.
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