Problems of Japanese Wisteria

Vine Fails To Flower because of Plant being Too Young
Wisterias are notorious for reluctant blooming. Many types take 10 to 15 years to flower for the first time. For this reason it is not advisable to grow these vines from seed or to acquire plants from an unreliable source. The best way to assure timely flower production, 2 or 3 years after transplanting, is to purchase stock developed from stem cuttings from plants known to be early bloomers. These vines will likely be several years old at time of purchase. In cases where long-established vines are still not blooming, experts suggest, but do not guarantee, that digging to expose the vine's roots and pruning them stimulates flowering. They also recommend feeding the vine super phosphate, pruning vegetative growth even more severely than usual, and skimping on water and fertilizer.

Leaves Curled And Distorted caused by Aphids
Aphids, also called "plant lice," are soft-bodied, pear-shaped sucking insects about the size of the head of a pin. They gather in clusters on leaves and tender buds of wisteria and suck cell juices. Their feeding retards and weakens plant growth. Infested wisteria leaves may turn yellow or brown. They wilt under bright sunlight, or sometimes curl and pucker. Spray the insects with insecticidal soap every 3 to 5 days. For persistent problems spray plant foliage and pests with neem insecticide 2 or 3 times at 7 day intervals. For more information see the files on Controlling Aphids

Leaves Skeletonized due to Rose Chafers
These beetles can be readily distinguished from other beetles by the grayish or fawn color of their 1/2-inch-long bodies and by their slow movements. They sometimes feed on wisteria, skeletonizing leaves and damaging flowers, especially white ones. They soil flower petals with excrement. Rose chafers (aka "rose bugs" or "rose beetles") appear suddenly, damage plants for from 4 to 6 weeks and then disappear suddenly. Handpick visible beetles and drop them into a jar of soapy water to drown. For major infestations spray beetles with a pyrethrum insecticide, in encapsulated form, if possible. Do this late in the afternoon to avoid harming beneficial insects and honeybees in the area. For long-term control, scratch milky spore powder (Bacillus popillae) into the soil to kill chafer grubs.

Small Bumps On Leaves And Stems means Scale Insects
Scale insects form groups of small bumps or blister-like outgrowths on vine stems and leaves. These are waxy shells that protect the insect feeding beneath. These shells may be white, yellow, or brown to black, and are about 1/10 to 2/5 inch in diameter. The first sign of a scale attack is often discoloration of upper leaf surfaces, followed by leaf drop and reduced growth. Heavy infestations kill plants. Some species excrete honeydew, which coats foliage and encourages ants and sooty mold growth. Some scale can be pruned off when excess vegetation is periodically cut back. Spray vines and foliage with light (superior) horticultural oil when scale is discovered. It will coat plant surfaces and smother the pests. For more information see the file on Controlling Scale

Leaves Mottled, Distorted indicates Mosaic Virus
Viruses are transmitted to wisterias by aphids. The first symptom is usually a yellow spotty discoloration, a "mottling" or "mosaic" pattern on the leaves. Eventually the plant dies. There is no cure, and infected vines should be removed. Prevent virus outbreaks by controlling aphids, keeping weeds down, and sterilizing tools used for pruning other plants or cutting flowers.

Leaves Covered With White Powder caused by Powdery Mildew
Powdery mildews are caused by fungi that live on the surface cells of plants, not inside them. Infected wisteria leaves are covered with a white or ash-gray powdery mold. Badly infected leaves become discolored and distorted, then drop off. Powdery mildew thrives in both very humid and very dry weather. While it is unsightly, it is not life threatening to a mature, well-established wisteria vine. Spray affected plants thoroughly with wettable sulfur once or twice at weekly intervals starting as soon as the whitish coating of the fungus appears. Collect and discard all aboveground refuse in the fall to deny the fungus a place to over winter. For more information see the file on Controlling Fungal Disease

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