Why Does My Willow Look Unhealthy?

Are the leaves curled, and distorted, clusters of small insects are present on leaves and bark?

Do the leaves have holes, twigs may be girdled, silky bags hang from the branches?

Does the trunk and the branches have holes, tree look weakened, twigs may be dropping?

Are the leaves eaten, conspicuous tawny egg masses are present?

Are the leaves damaged on the undersides?

Are the leaves pale, mottled, and dropping early?

Are the leaves discolored?

Are the leaves skeletonized?

Are the leaves covered with white powder?

Do the roots, trunk, or branches have swollen, tumor-like growths on them?

Are the leaves pale on their upper side and are there any dusty blisters on the undersides?

Distorted, curled leaves are caused by aphids. These tiny insects can vary in color, green, pink, black, gray to completely white. They cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted, and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Adult male bagworms are black, clear-winged moths. Wingless females and larvae (caterpillars) live in distinctive 2-inch long bags of tough silk, camouflaged with bits of vegetation that hang from willow branches like ornaments. Handpick and destroy all the bags. If you notice crawling caterpillars you may have to use insecticide as they are really hard to get rid of.

Numerous borers attack woody plants, mining the inner bark and wood of branches and trunk. Prune off borer-infested branches. If you see borer holes in your trees, probe into them with a flexible wire or inject a solution of parasitic nematodes. After treatment, seal holes with putty.

Gypsy moth caterpillars sometimes mass on the foliage and devour it, defoliating the tree. The tree may die after repeated defoliation. Mature caterpillars have 5 pairs of blue spots and 6 pairs of red spots along the back. In light infestations destroy eggs or pick caterpillars by hand, in more severe cases spray plants with BTK or pyrethrin as the last resort.

Imported willow leaf beetles are metallic blue beetles, about 1/8 inch long. They live through the winter under the bark scales and in the rubbish around willow trees. Their worm-like grubs feed on the undersides of willow leaves, leaving only a network of veins. Clear all debris around willow trees. Spray the tree with pyrethrin if the infestation is severe.

Willow lace bugs are small square-shaped bugs, 3/16 inch long or less, with elaborately reticulated wings that resemble lacework. They cause leaves to turn yellow, then brown, and eventually die. Treat plants with a commercial pyrethrin spray or dust if the damage is severe.

Discolored willow leaves are caused by thrips. Thrips are tiny, yellow to black flying insects. They hide under leaves. Severely infested plant parts should be pruned off and destroyed. Control thrips by introducing lady beetles or lacewings. Insecticidal soap helps in severe infestations.

Adult willow shoot sawflies are wasp-like, but with thicker midsections, 5/8 to 1 ½ inch long. They have 2 pairs of transparent wings. Their larvae resemble caterpillars, and are, on the average, 1/2 inch long. Remove them by handpicking or with blasts of water. For heavy infestations, use insecticidal soap spray.

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants 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.

Bacterial disease Crown gall causes wartlike swellings. Gall bacteria are introduced into trees that are vulnerable due to wounds. If the plant is only slightly infected, prune off diseased growth. Cut down and destroy any severely affected trees.

Likely cause for these symptoms is a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

Willows have weak, brittle wood. They often split or break in storms, especially under the weight of ice or wet snow. There is no effective protection from this problem, except to site the trees in areas that are somewhat sheltered from the wind.