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Insects on Juniper Trees

Utah Juniper (Juniperus osteosperma) in red sand desert image by Lars Lachmann from

There are numerous species and sub-species of juniper trees (Juniperus) throughout North America, Europe and Central America. The trees have been used for food, fuel, shelter, natural medicines and even the production of wine. Junipers are highly resistant to disease and only a few insects pose a pest problem for the hardy trees. Some Junipers are more than 1,000 years old, according to the U.S. National Forest Service. Most junipers will attain a height of 33 feet, but there have been specimens recorded that measure up to 87 feet tall.

Juniper Bark Beetle

The juniper bark beetle (Phloeosinus serratus) thrives during times of drought. The beetles normally attack only weakened juniper trees unless the climate conditions are exceptionally dry. A healthy juniper tree will naturally produce an abundance of sap to push the burrowing beetle out of its bark at the first sign of infestation, but in times of drought, the trees sap production is seriously compromised so even a healthy tree is at the mercy of the juniper bark beetle.

Control of the Juniper Bark Beetle

When a juniper bark beetle successfully invades the juniper tree, there is no way to control the insect. The beetles damage the tree with their borrowing and also by transporting a fungus known as the "blue-stain" fungus. Cutting infected trees down and promptly disposing of them by burning or drying out the fallen tree is the only means of control to keep the beetles spread minimized. Carbaryl and permethrin-based insecticides can be used to prevent junipers from becoming infected with the juniper bark beetle.

Gall Midges

Several species of gall midges affect juniper trees around the world. Adult gall midges lay eggs in the trees new growth and produce what is known as a gall. Galls are an abnormal area of growth on the tree, which is caused by the invasion of the midge into the new growth. The larvae flourish by burrowing into the new growth. After feeding the larvae leave the gall and burrow deep within the soil at the base of the tree. They will emerge in early June as full grown beetles. A few species of gall midges produce four to five generations of beetles in one season.

Control Of Gall Midges

Hand removal of the galls produced by the insects before the larvae hatching has shown success. Chemical control is easily obtained by using Bayleton or Daconil 2787 insecticides. Follow the directions on the label for application at seven- to 10-day intervals.

Juniper Berry Mite

Utah Juniper image by Carol Hyman from

The juniper berry mite (Trisetacus quadrisetus) is an insect that feeds heavily on the berries of the juniper tree. A heavy infestation can destroy virtually every berry on the juniper tree, according to the United States Department of Agriculture. The mite forms a gall around the berries and then burrows within the blue berry to eat voraciously. Control is similar to the control of the gall midge. Use of insecticide proves successful.

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