The Wisteria genus consists of deciduous vines that are pruned and grown as shrubs or trees. Depending on the species, wisteria grows in U.S. Department of Agriculture plant hardiness zones 4 to 9 and produces clusters of showy blooms that may have a pleasant fragrance. Various species of insects -- both problematic and beneficial -- visit wisteria but rarely cause major damage.
Both soft and armored scales attack wisteria, causing various degrees of damage to the plant. Scales typically appear as bumps on foliage and stems, and most people don’t initially realize this pest is an insect. Adult females and immature scales are wingless and have an oval, round or elongated body with a humped appearance. Adult male scales are small, winged insects that generally don’t feed, are rarely seen and live for only a few hours. Female and immature scales feed on juices running through wisteria, leaving the foliage wilted, discolored and distorted. Their feeding eventually results in premature leaf drop. Narrow-range oil -- such as horticultural oil -- thoroughly applied to the plant at some point from late winter through early summer helps prevent scales.
Aphids and Mealybugs
Aphids and mealybugs are unfortunately common pests in gardens. These sap-sucking, soft-bodied insects insert their slender, stylet mouth into tender areas of the plant and consume the vital cell content coursing through the wisteria. Aphids congregate on the underside of leaves and have green, yellow, red, brown or black bodies with a wooly or waxy appearance. Female mealybugs appear as small pieces of cotton on leaves and stems of the wisteria, but winged male mealybugs are tiny and rarely seen on plants. Aphids and mealybugs secrete honeydew, which results in sooty mold. Sooty mold is a sootlike, black fungus that covers leaves and stems. Even though sooty mold only affects the look of the wisteria plant, it can interrupt the leaves' photosynthesis process. Small infestations of aphids and mealybugs generally won’t cause serious damage for which chemical control is warranted. Larger infestations may require chemical control with neem oil, insecticidal soap or horticultural oil.
Roundheaded borers -- sometimes called longhorned beetles -- can attack wisteria, causing holes in the plant's bark. Stains and liquid oozing from trunks and limbs are common symptoms of borer damage. The leaves can wilt and discolor, stem dieback occurs and -- in extreme circumstances -- the entire wisteria plant is killed. Adult roundheaded borers have an elongated, brightly colored, beetlelike appearance with long antennae. Insecticides are not an effective control against these pests, so keeping the wisteria vigorous and healthy is the best defense , according to the University of California Statewide Integrated Pest Management Program. Thankfully, these borers generally only attack plants that are damaged or dying. Prevent injury to the wisteria, and remove damaged, diseased or dead limbs from the plant to avoid attracting borers. Furthermore, never place freshly cut wood next to wisteria, because the roundheaded borers can emerge from the cut wood and infest the nearby plants.
Wisteria is a host plant for the larvae of the silver-spotted skipper. This butterfly has a short, rounded tail and brown wings and body, with a row of yellow to gold spots located in the middle of the forewing. These spots are visible on the top and underside of the wing. A large, white, irregular-shaped patch is located on the underside of the wings. Silver-spotted skipper eggs are green with a reddish top. The larvae measures about 2 inches long with a yellow abdomen wrapped in dark spots and stripes. Its deep red-brown head has large yellow eyes. Like other butterflies, the silver-spotted skipper helps provide a balanced ecosystem within your garden. Butterflies attract birds and other beneficial insects, wildlife and invertebrates that keep unwanted insects under control.
- Fine Gardening: Genus Wisteria
- University of California Statewide Integrated Pest Management Program: Wisteria — Wisteria Spp.
- Missouri Botanical Garden: Wisteria Frutescens
- Missouri Botanical Garden: Wisteria Floribunda "Multijuga"
- University of California Statewide Integrated Pest Management Program: Scales
- University of California Statewide Integrated Pest Management Program: Aphids
- University of California Statewide Integrated Pest Management Program: Mealybugs
- University of California Statewide Integrated Pest Management Program: Roundheaded (Longhorned) Borers
- University of Florida IFAS Extension: Silver-Spotted Skipper; Epargyreus Clarus (Cramer)
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