According to SFGate, a couple of diseases could cause a wisteria to die, the more serious being canker disease. This disease destroys the foliage of the plant and leaves dark lesions. Prune infected vines immediately to prevent spread of the disease. Keeping the plant hardy also helps to prevent canker problems.Continue Reading
The tobacco mosaic virus causes wisteria foliage to develop a mottled discoloration. The virus spreads easily and there is no cure for it. Prevent this virus by planting resistant varieties of wisteria. If infected vines are noted, destroy them immediately.
Two species of scales affect wisteria. These tiny, hard-shelled insects attack the vines. The calico scale has a light brown cover. As these insects feed on the wisteria, they secrete a sugary substance known as honeydew. Honeydew causes disease to the vine and attracts ants that do further damage. The second type of scale, the wisteria scale, is darker than the calico scale. It attaches to the vine to feed. High-quality horticulture oil protects the wisteria from both types of insect. Lacewings and parasitic wasps are natural predators for scales and present an organic solution to the problem.
If the dying wisteria is a recent addition to the garden, graft problems are a potential reason for it to die. Nurseries propagate wisteria through grafting. If the graft is not healthy, the plant dies.Learn more about Outdoor Plants & Flowers