Why Does My Wisteria Look Unhealthy?

Are the leaves covered with white powdery patches?

Are the leaves yellow, stems, and leaves are covered with small bumps?

Do the leaves and stems have black to brown spots on them?

Do the vines or the roots have swollen, wartlike growths on them?

Are the vines and the branches of your wisteria oozing sap through the lesions?

Does the woody parts of the vine have small holes in them, limbs may die or break off?

Do the leaves have notched edges?

Does the whole vine declines, leaves are stunted and pale and there is no new growth?

White, powdery coating on the leaves is caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected vines by thining them. Water wisteria from bellow to keep foliage dry. Any affected leaves should be cut off and removed. Any commercial fungicidal spray will protect your plant from further infections.

Yellow leaves covered by small bumps are caused by Wisteria scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

If your wisteria leaves have black to brown spots on them they are most likely fungal leaf spots. Remove and destroy all infected leaves. Thin vines to increase airflow. Water wisteria from below to keep foliage dry. Clean up all plant debris around wisteria to remove overwintering sites.

Bacterial disease Crown gall causes wartlike swellings on roots, stems, and branches of many trailing plants. If your wisteria is only slightly infected, prune off diseased growth. Severely infected plants can only be removed and destroyed.

Oozing lesions are caused by cankers. Cankers can be caused by several different kinds of fungi. Mildly affected plants will recover if you remove and destroy all affected branches. Heavily affected plants can't be cured and you should remove the whole plant. Avoid damaging your plant with lawnmowers, trimmers, or pruning tools because the wounds are the best place for cankers to start.

If the woody vines have small holes in them the culprits are Wisteria borers. These small insects attack wisterias by mining the inner bark of the vines' woody parts. Control is difficult, so your best bet is to properly water and feed your wisteria if the infestation is small. Borers seek out plants that are stressed or weak and usually avoid the healthy ones. If you see borer holes, probe into them with a flexible wire or inject a solution of parasitic nematodes. After treatment, seal holes with putty.

Notched edges on the leaves are caused by Black vine weevils. The wingless, black bugs with yellow markings are adults that feed on the leaves. To control them, spread a drop cloth around your plant and shake it so the adults drop. You can get rid of them after that. Spray leaves several times with pyrethrin for major infestations.

Root rot can be caused by overwatering or by poorly drained soil. Early in this disease, decreasing watering may be enough to save your plant. As the disease progresses, you may have to dig the plant, trim the roots back to healthy tissues and replant it in a very dry location, watering only when the top two inches of soil feels dry to the touch.

Graft failures are common problems for wisterias. They may occur in plants as old as 20 years, due to a graft that was only ever partially compatible. Older plants may not be saved, but younger plants can sometimes be regrafted onto a vigorous rootstock if they’re pruned back aggressively.