Gage County
1115 West Scott St.
Beatrice NE 68310
Phone: (402) 223-1384
FAX: (402) 223-1370

Spruce Spider Mite (Oigonychus unungis)

The spruce spider mite is one of the most important pests of fir and many other conifers. It sucks sap from the undersides of needles, causing the stippled appearance. Spruce spider mites usually first appear in March or April. These cool -weather mites do most of their damage during spring and fall, becoming dormant during hot summer weather when the Two-Spot Spider mite becomes active. Mites can rapidly build up to tremendous numbers during the growing season. Young fir trees may die the first season. If mites are left uncontrolled over a period of years, older trees die progressively from the lower branches upward.

Mite symptoms on conifers:
Yellow stippled needles, dirty, dusty webs, brown needles on lower branch tips and needles dropping off the lower branches are all symptoms of Spruce Spider Mites. Most of the discoloring appears on the underside of the needles near the stem end of the needle. These symptoms occur during the cool weather of the spring or fall with the summer heat showing up damage done while it is cool.

If you suspect Spruce mites, you can check for them by holding a piece of white paper under the suspected branch, pound down on top of the branch and check the paper for small black specks, like black pepper, on the sheet of paper. Hold the paper in direct sunlight and watch for the specks to move around, movement could mean mites. If you take your finger and press on the specks and slide your finger, Spruce mite will leave a smear or streak on the paper.

Possible control measures:

• High pressure stream of cold water from garden hose directly on branches starting at the top of the tree to the base. Wash the tree throughly.
• Use Isotox or Kelthane spray early spring about when the saucer magnolia blooms and again 7 to 10 days later. Then check for spider mites using the above white paper method.
• Insecticidal soaps or oils. Do not use oils on blue pigment trees, the oil will coat the blue color and turn the trees green and they will lose the blue color. New growth will be blue so you will have green and blue trees.

Possible hosts: All types of spruce, pines, juniper, arborvitae, hemlock and yew.

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