Most Common Tree Insects

Birch Leafminer

This insect can be very damaging to birch foliage in May and June. It causes brown patches on leaves which expand and can kill them entirely. Repeated defoliation can tax the vitality of young birches. Damage can be prevented with several methods of treatment to maximize effectiveness and minimize environmental impact.

Honey Locust Plant Bug

High populations of this insect have been found across the metro area in recent years. Outbreaks can defoliate a mature tree within weeks after leaves emerge in late spring. Control of this insect can be achieved in a variety of manners.

Scale Insects

Several species of scale insects damage many common landscape plants. Scale insects attach themselves to a plant beneath a protective cover, making control more difficult. They feed on sap, reducing plant vitality and causing dieback. Treatment must be tailored to the species of scale insect.

Mites

Mites can be found on nearly every coniferous plant in the landscape. Mite populations can explode in a single season with hot dry conditions, turning interior foliage yellow to rust-brown. With established populations, a long-term treatment and monitoring program needs to be maintained for adequate control.

Sawflies

Sawflies are very damaging to mugho pines. They can also affect other pine and spruce trees by consuming needles in feeding groups. This insect can disfigure and shorten the life of a young spruce or pine. Treatment and properly-timed monitoring can easily control this insect.

Spruce Gall Adelgids

Adelgids are insects whose feeding stimulates gall formation in spruce trees. The galls resemble pineapples and shelter young insects. Gall formation can make a young tree unsightly and can kill branches. A single spray treatment in the early spring provides effective control.

Two-Lined Chestnut Borer in Oaks

Damage from this insect, which is attracted to stressed oak trees, can be difficult to distinguish from oak wilt and drought stress. Two-lined chestnut borer feeding causes branches to thin and die back. Control often requires multiple insecticide applications coupled with removal of infested limbs.

Bronze Birch Borer

Birch trees in the urban environment are often stressed, attracting this insect. Bronze birch borer larvae feed on the inner bark, causing the canopy to thin and die back. A comprehensive treatment plan should include insecticide applications, regular fertilization, mulching and pruning to remove infested branches.

Aphids

Aphids can damage a variety of landscape plants by curling and distorting leaves, stunting growth and causing chlorosis (yellowing of leaves). This insect can be very damaging to plants when populations go unchecked. Monitoring and spray treatments are effective for control.

Ash Flower Gall Mites

A conspicuous aesthetic problem found in many ash trees. Mite activity stimulates the formation of green colored galls that turn brown and persist. Galls are chiefly an aesthetic problem but can cause a decline in the health of heavily infested trees. Control of the flower galls is difficult, and most treatments focus on increasing the vitality of susceptible trees.