Tree & Shrub Care Insect Control

At any given time during the growing season, if you look closely at your trees and shrubs, you will be able to find insects present. But, most of those insects are harmless, or even beneficial to the tree. Most insects cause damage for just a short time each year. However, some insects can cause serious damage or death if conditions are right.

Inspect pests can be grouped into two major categories:

• Those that feed on leaves
  
• Those that invade bark and trunks

Leaf miners are very small insects that get between the upper and lower surfaces of a leaf. They feed on the lead tissue inside of the leaf, and leave either serpentine “mines” winding throughout the leaf, or brown blotches where the inner leaf tissue has been removed. You may also see small black particles between the leaf tissue, which is the insects’ fecal matter, or frass. There may be only a few leaves on a tree or shrub affected, or the tree can turn brown if there is a heavy infestation, Oaks, hawthorns and birches are most often attacked by leaf miners. Heavy or repeated infestation may not kill the plant outright, but may take it more susceptible to other problems.

Chewing insects will eat entire parts of the lead. They can feed on the edges of leaves, chew holes in the centers of leaves (“shotgun” holes), skeletonize the leaf (eat tissue between veins), or “window feed” (eat away only the upper and lower surface of the leaf).

Sucking insects feed on plants by sucking the juices out of leaves or stems. Common sucking insects are aphids, scale, and mites.

Scale often feed on twigs and stems of plants, can cause the plant to look off-color and /or show early fall color. Scale come in a variety of sizes, shapes and colors. The adult stage is usually a somewhat hard-shelled or cottony “bump” on twigs that are immobile and can be often controlled by dormant oil sprays. Young scale, called “crawlers”, is present for a short time each year but are more susceptible to pesticides because they lack the hard shell protection adults have. Ladybugs are natural enemies of aphids and scale. Scale activity is common on maple, ash and oak trees, laurel.  Euonymus and privet.

Mites attack almost all trees and shrubs. Plants that are stressed, particularly by heat or drought, are especially susceptible to mite infestation. Mites are very small and usually feed on the undersides of leaves. Shaking a leaf over white paper may dislodge them, and you eill see what looks like moving dust on paper. They may be red, black, gray, or some other color. Leaves damaged by mites tend to look silver, bronze or yellow.

Galls are unusual growths that form on the upper or lower surface of leaves. They can be round or irregular shaped bumps, small pouches, or “spindles”, and they found in variety of colors, including red, purple, green, black, and orange. These deformities are typically caused by feeding or egg laying of one of a variety of insects. While unattractive to us, galls rarely cause any harm to the plant. To reduce insect numbers for the following year, rake and destroy infected leaves in fall.

Bark and trunk invaders include borers that get into or below the bark and tunnel around in the wood. Most borers are not a problem on healthy trees, but act as “secondary invaders” attacking trees that are already weakened from some other reason.