How Should I Deal With Insects Attacking My Birch Tree?

Do you have problems with Birch leafminers - flat, white larvae of a sawfly that feed between the upper and lower leaf surfaces?

Do you have problems with Birch leaf skeletonizers - small light green caterpillars that chew twisting mines in birch leaves in mid-summer?

Do you have problems with Japanese beetles - metallic-brown beetles that devour leaves giving them a characteristic skeletonized appearance?

Do you have problems with Fall webworms - small hairy white caterpillars that live communally in thin silken webs at the ends of branches?

Do you have problems with Redhumped caterpillars - large, a yellow caterpillar with black and white stripes and red head?

Do you have problems with Eastern tent caterpillars - hairy black caterpillars with a white stripe down the back, that live communally in silken tents?

Do you have problems with Fall cankerworms - green, looper caterpillars that make holes in leaves, often making extensive damage?

Do you have problems with aphids - tiny insects that cause distorted, yellow leaves?

Do you have problems with San Jose scales - small circular brown armored insects that have a series of dark concentric rings on their waxy covering?

Do you have problems with Oystershell scales - 1/10 inch long insects that resemble crusty accumulations of oyster shells on the bark?

Do you have problems with Lace bugs - flat, dark-colored insects with lacelike wings that feed on the undersides of leaves?

Prune off and destroy all infested leaves. Remove debris in fall because it might contain overwintering leafminers. Introducing parasitic wasps is a very effective method of controlling leafminers. Chemical control is usually ineffective.

Spray your tree with Bacillus thuringiensis (BTK) and make sure to get to both the upper and lower side of the leaves. Raking and destroying fallen leaves will help to reduce the damage the following year.

Handpick adult beetles into a can of soapy water but make sure to wear gloves as Japanese beetles are blister beetles. Apply parasitic nematodes to the soil to limit beetle grub populations. Use pyrethrin powder or neem oil as a last resort.

Fall webworms are usually held in check by songbirds, yellow jackets, wasps, and rodents. You can easily remove the webs when they occur in trees. Insecticides are seldom necessary for fall webworm, especially in trees, and should be considered only if the infestation is heavy. Bacillus thuriengensis (BT) can be used when the caterpillars are small, but it will not provide satisfactory control once the webs are large.

Biological control and spot-pruning of infested shoots are sufficient to manage this pest in most situations. Insecticide application can be warranted if caterpillars are abundant and their feeding damage is intolerable, especially when trees are small, already stressed, or unhealthy from other causes.

Tent caterpillars can be controlled by manually destroying their nests or egg cases, spraying leaves with BTK at the first sign of damage, or applying pyrethrin spray as a last resort.

Fall cankerworm populations are usually held in check by natural enemies, but if they do become problematic larvae can be hand-picked from the plants. The application of BTK will effectively kill younger larvae.

Aphids 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.

Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

Treat plants with a commercial pyrethrin spray or dust if the damage is severe. Prevent problems by covering plants with row cover until they blossom.

If you have problems with borers, insects that mine the inner bark and wood of branches and trunk, prune off 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.