Common Insects That Attack Juniper Trees and How to Control Them

Overview

Juniper trees (Juniperus) thrive across North America, Europe, and Central America. Valued for food, fuel, medicine, and even wine production, these hardy evergreens can live over 1,000 years and reach heights up to 87 feet. While naturally disease-resistant, a few insects pose serious threats.

Juniper Bark Beetle (Phloeosinus serratus)

This beetle thrives during drought. Healthy junipers typically push invaders out with sap, but water stress cripples this defense, leaving even vigorous trees vulnerable. Once inside, beetles tunnel through bark and introduce blue-stain fungus, compounding damage.

Control

No cure exists for infested trees. Immediate removal and destruction (burning or thorough drying) of infected wood limits spread. Preventive sprays with carbaryl or permethrin-based insecticides protect healthy trees.

Gall Midges

Multiple species lay eggs in new growth, forming galls—abnormal swellings where larvae feed. After maturing, larvae drop to soil and emerge as adults in early June. Some species produce four to five generations per season.

Control

Hand-remove galls before larvae hatch. Chemical options include Bayleton or Daconil 2787, applied at 7- to 10-day intervals per label directions.

Juniper Berry Mite (Trisetacus quadrisetus)

These mites destroy berries by forming galls and burrowing inside to feed. Heavy infestations can eliminate virtually all fruit on a tree.

Control

Similar to gall midge management: insecticide applications prove effective.