What Is Wrong With My Poplar?

Does the trunk or the branches have swollen sunken lesions?

Are the leaves spotted, brown, and drop prematurely?

Are the leaves covered with white powder?

Are there any silky caterpillar tents in the branches in late summer?

Do the roots of the poplar rise above the soil level?

Various fungi cause elongated, dark sunken cankers, or sores, in poplar trunks, limbs, and twigs. It may also attack leaves early in the growing season. Sometimes the sores ooze infecting spores that spread by splashing rain, birds, and insects to infect new sites. Cankers may eventually girdle branches and whole trees. Because some cankers primarily attack weak trees, the most effective prevention is to keep trees vigorous by feeding, watering, and controlling insects and fungus parasites of the leaves.

Spotted leaves on poplars usually indicate fungal leaf spot. Some fungal spots are surrounded by flecks or black dots, their spore-bearing fruiting bodies. Often spots come together to form larger patches of dead tissue. Pick off and discard infected leaves. Remove dead leaves to reduce overwintering spore populations.

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. Spray foliage thoroughly with wettable sulfur once or twice at weekly intervals starting as soon as the whitish coating of the fungus is visible.

Fall webworm is a caterpillar that makes filmy looking tents very similar to those made by Tent Caterpillars in the spring. Fall webworms are usually held in check by songbirds, yellow jackets, wasps, and rodents like mice eat the caterpillars and pupae. You can easily remove the webs when they occur in trees around the home. Insecticides are seldom necessary for fall webworm, especially in trees, and should be considered only if the infestation is heavy. The insecticide Bacillus thuriengensis (BT) can be used when the caterpillars are small, but it will not provide satisfactory control once the webs are large and conspicuous.

Poplars are vulnerable to living in compacted soils. When that happens they produce surface roots on top of the soil. Cover the surface roots with "light" soil (topsoil mixed with peat moss or sand). Don't cover the roots with much more than about 2 inches of soil.

Because poplars grow so fast, their wood is weak and brittle. Once they reach maturity they quickly become vulnerable to wind and weather damage.