How2Day: What Type of Bugs Are Affecting My Shrubs?

Aphids live in colonies on the stems of shrubs and other plants. Geostock/Photodisc/Getty Images
Insects can cause defoliation, bark damage and stunted growth of shrubs if not treated promptly. Maintaining the health of the shrub through regular watering and fertilizing can help prevent widespread destruction by many pests. Shrubs subjected to drought, nutrient deficiencies, improper pruning or severe climatic changes become more susceptible to insect damage.

Foliage feeding insects cause damage to shrubs by consuming the leaves. They chew and skeletonize the tissue of the leaf causing it to have a ragged, hole-riddled appearance. A wide array of insects do the most damage in their larval, caterpillar or worm stage, but numerous adult beetle varieties can also cause widespread destruction.

Leaf feeding beetles utilize their chewing mouths to consume the foliage. The June beetle, blister beetle and cottonwood beetle all consume the leaf's tissue. Fall and spring cankerworms, prairie tent caterpillars, birch leafminers and the elm sawfly all eat the foliage of shrubs. Grasshoppers also enjoy feasting on foliage.

Identify the offending pest prior to utilizing pesticides. Many insect varieties require specific pesticides applications at certain times to be effective.

Sap sucking insects pierce the stems, leaves and new growth of the shrub to suck its nutrients. They can cause the shrub to lose its foliage, produce deformed new growth, suffer yellowing discolorations and fail to thrive.

Aphids, scales, spider mites and leaf hoppers all consume the shrub's sap. Aphids and spider mites usually congregate on the shrub's new growth or beneath its foliage in colonies. The small insects produce a honeydewlike substance that will often attract ants on the shrub who enjoy consuming the honeydew. The honeydew will also cause the shrub to suffer black mold and discoloration.

Leaf hoppers cause the foliage of the shrub to become spotted with yellow or brown damage from their feeding. The small, white, hopping insects can also spread viruses, according to North Dakota State University. Scale insects appear as small tan or gray spots on the shrub's stems. The insects lay beneath a waxy covering where they attach their mouths to the plant's tissue to suck the sap.

Wood boring insects are generally the larvae of beetles such as the ash, lilac, poplar and bronze birch borer beetle. The eggs are laid on the shrub's stems and the larvae, upon hatching, burrow beneath the plant's bark. The insects will cause holes to occur in the shrub's bark. If the shrub's bark is peeled back, the gardener can observe trails or a diverse tunnel system caused from the borer larvae's feeding activity.

Gain control of the borer by identifying the adult prior to it laying eggs. If the adult is treated before laying the eggs the gardener will be better able to prevent damage from occurring. Pesticides are rarely effective when the larvae have burrowed into the shrub's bark. Infected branches can be pruned away and disposed of if the infestation is not too severe.

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