Chewing Insects

Defoliating insects migrate to the foliage of a tree and feed on the leaves. Other chewing insects attack the fruit. Caterpillars and beetles make up the largest proportion of chewing insects. Generally, trees can bounce back from an attack of these defoliators, though repeat infestation will weaken a tree and can eventually kill it by starving it of energy.

Examples

Spring and Fall Cankerworm, Tent Caterpillar, Gypsy Moth, Leafminers, Bagworm, Japanese Beetle, Apple Maggot, Cherry Fruit Worm

Control

Healthier trees are less likely to become infested, so maintaining the strength and vitality of your tree is an important prevention step. Once chewing insects are present, controlling movement up and down the stem with physical barriers can interrupt the lifecycles of many caterpillars. Insecticides can be used to kill the insects.

Recommended Products

Prevention

  • TreeHelp Bug Bands are an effective tool to help control the movement of caterpillars from tree to tree as well as those that migrate up and down a tree trunk.

  • TreeHelp Annual Care Kits are helpful in promoting the overall health of a tree so that it can withstand the impact of an insect attack.

Treatment

If a tree has been attacked by chewing insects there are a number of effective sprays and controls that can be utilized to control the insects.

  • Safer Caterpillar Killer Concentrate is a safe and effective solution for controlling caterpillars and other leaf-eating insects on shade trees, ornamentals, and evergreens. It utilizes BTK (Bacillus thuringiensis var. Kurstaki), which kills caterpillars after ingestion, reducing defoliation and protecting new growth. Reapply every 7–10 days as needed for ongoing control.

  • Garden Insect Spray with Spinosad is a new insecticide that is similar to BTK and also made from a natural soil fungus. Spinosad, however, is less sensitive to UV breakdown than BTK and therefore only needs to be reapplied every 3 to 4 weeks. Spinosad is approved for organic gardening.

  • Bug Buster is a stronger spray made from a synthetic pyrethrin. Bug Buster is recommended when a tree is under attack by a variety of chewing and sucking insects and is an effective treatment against a wide range of insects.

  • In some cases, due to the size of the tree, spraying is not an option. In these cases, there are two effective options:

    • Multi-Insect Killer Tree Injection Kit is injected directly into the tree's trunk and gets throughout the tree in about 72 hours.

    • Once-A-Year Insecticidal Soil Drench w/Merit is applied by watering the treatment right on to the tree's roots. The insecticide is then taken up through the tree's roots and dispersed throughout the tree. This normally takes about 3 weeks and provides protection for the tree for a full year.

Traps can also be used to reduce the local population of the attacking insect: