Insects on tree bark are treated according to what they are: scale on the bark is smothered with horticultural oil, caterpillars and ants climbing the trunk are caught with a sticky band, and borers tunneling into the wood need a systemic insecticide. Identifying the insect comes first, because each group is reached in a different way.

How can the insects on the bark be identified?

By what they leave behind and how they move. Three groups account for most bark insects:

• Scale insects: small raised bumps on branches and twigs, often with a sweet, sticky residue called honeydew nearby.
• Borers: entry and exit holes in the bark and small mounds of sawdust at the base of the tree.
• Crawling insects: caterpillars, ants, and similar pests moving up the trunk.

How are scale and climbing insects on the bark treated?

The scale is smothered where it sits, and climbing insects are stopped before they reach the leaves. Spraying Horticultural Oil Insect Spray onto the leaves and bark kills scale by blocking the insects' pores. Where caterpillars or ants are climbing the trunk, a TreeHelp Bug Band Protective Insect Barrier tied around it in late fall and early spring traps them as they try to cross.

How are borers inside the bark treated?

With a systemic insecticide, because borers feed on the vascular tissue inside the trunk and a systemic treatment travels through that same tissue. To reach borers already inside an ornamental tree, the Multi Insect Killer Tree Injection Kit is injected through holes drilled at the root flare, where the trunk widens at ground level. The guide to boring insects covers prevention as well.

Frequently Asked Questions

Is there one treatment for both borers and scale?

Yes. The injection kit controls both borers and scale insects, though it should not be applied to food bearing plants such as fruit trees.

When is horticultural oil sprayed on bark?

In two seasons. It is mixed at 1:50 for a dormant spray in non freezing weather, or at 1:100 during the growing season.

How can borers be kept off a tree in the first place?

By keeping the tree strong and healthy. Borers usually attack weakened or stressed trees, so proper watering and fertilization make a tree less of a target.

Does the injection kit work on evergreens?

Not reliably. Injections into conifers may be slow to take up or not taken up at all.