Prized as "one of the most splendid deciduous vines any gardener can grow," according to the Washington State University Extension, wisteria is a vigorous, fast grower. Though wisteria provides showy interest in the home garden with flowers in soft shades of violet, blue and pink, it is no stranger to problems that can result it its demise. Examine your plants regularly to keep problems like pests and disease from killing your garden vines.
Provide consistent care to your wisteria for healthy, vigorous vines that have a greater capacity to avoid and overcome pest and disease problems. Grow wisteria in areas that offer full sun exposure as sun deficiencies can result in bloom problems. Maintain moist, well-drained soil with an acid pH for best growth. Prune severely and regularly as wisteria will cover and compete with other plants in the garden. Prune any time, including just after flowering, to promote bloom. Irrigate to keep soil moist while plants are immature. Once established, however, avoid irrigation unless soil becomes dry and resist the desire to fertilise as it can reduce flowering.
Roundheaded borers, also referred to as longhorned beetles, are pests of the wisteria plant. Displaying long antennae, as their name suggests, these pests have red, brown or black bodies. In their larval, or immature, stage they exhibit similar colouring though they resemble worms and measure approximately 3 1/4 inch long. Borers often appear during spring.
Sooty canker is a fungal disease of wisteria vines that attacks branches. Caused by the fungal pathogen "Hendersonula toruloides," this disease invades wisteria plants through entry points, like wounds. Healthy, recently pruned vines are at risk as well, as sooty canker spreads sporadically in water and wind, landing on otherwise healthy plants. Expect this disease during summer.
Long-horned beetles bore into plants, eating as they tunnel through branches. Their tunnelling results in destroyed branches with leaves that wilt and become discoloured. These pests can kill parts of the plant or the entire wisteria, particularly when plants already experiencing diminished health.
Sooty canker leads to the wilting of wisteria foliage as well as branch dieback. Cankers, or depressed areas of dying plant tissue, appear on infected plants, beginning as a brown-hued wet area. As the disease progresses and spreads throughout the plant, it kills the wisteria vine within one to several years.
Control long-horned beetles on wisteria by removing and destroying affected plant parts. Avoid attempting the use of insecticides as they are ineffective. Speak with your extension agent about the best time to prune and how to treat fresh cuts to keep borers away as they target such areas of entry.
To control sooty canker on wisterias, prune and destroy infected plant parts to decrease disease intensity. Cut behind cankers, leaving only health plant material. Sterilise pruning shears between each cut to avoid disease transmission to other parts of the plant or other plants. Treat the cuts with a fungicide with the active ingredient copper to avoid the reinvasion of disease.