Spruce spider mites are most active in the cooler weather of spring and fall. To understand how to control them, you need to understand their life cycle. The mites lay eggs in the fall. The eggs overwinter under bud scales or at the base of needles and hatch in spring.
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The blue spruce tree (Picea pungens), named for its sharp-ended needles, is a coniferous evergreen member of the pine family also known as the Colorado spruce. This native of the Rocky Mountain area typically appears in landscapes, containers and rock gardens in U.S. Department of Agriculture cold hardiness zones 4 to 7. Blue spruces are susceptible to a number of disease and pest problems, most commonly fungal infections and insect overpopulation. If kept healthy, however, the trees can live for up to 200 years, reaching 70 feet in height at the top of their range.
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Examine the tree for needle cast fungus (Rhizosphaera kalkhoffii), which appears as yellowish or red needles covered with black spots, and causes defoliation. Prune the affected areas, disinfecting the equipment with 70 percent alcohol, and put all material into plastic trash bags. Apply a fungicide containing chlorothanlonil with a hand sprayer, applying it both when needles start to grow and when they finish growing. Wear safety gear like work gloves, goggles, a mask and long-sleeved clothing when spraying.
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Search for signs of other fungal infections, such as Cytospora canker. This disease affects the branches and trunk, causing them to die in a pattern that begins low in the branches. Prune away all affected branches, 4 to 6 inches below the cankers or, in some cases, all the way back to the trunk. Perform pruning in dry weather only to avoid spreading the fungus.
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Observe the tree for rust, which appears as orange spots on leaves and may cause them to turn yellow or brown. One rust variety, Chrysomyxa pirolata, only affects cones, causing them to lose seed viability. Treat rust by pruning away diseased branches, cleaning up all fallen needles around the base of the tree and disposing of them in plastic trash bags.
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Look for signs of insect infestations. Spider mites cause yellow or reddish dropping needles, while aphids cause galls. Treat both with insecticidal soap. Brown, sparse needles indicate white pine weevil infestations, which can be treated by pruning damaged sections.
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Identify pine needle scales on the tree, which create scab-like formations. Scales not only cause appearance problems, but drain trees of nutrients and may attract mold due to the abundance of honeydew. Treat scale infestations with horticultural oil during the dormant season.
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Watch for signs of bark beetle infestations, which can be extremely damaging to all trees in the area. Beetles, such as twig, spruce and engraver beetles, make a series of holes in the branches and trunks of trees. Once populations grow large, the trees cannot be saved and must be removed to prevent the infestation from spreading to other trees. Treat beetle problems early by enlisting professional help from a licensed pesticide applicator, as bark beetle pesticides are not available for home use.
Things You Will Need
- Pruning shears and loppers
- Isopropyl alcohol
- Plastic trash bags
- Fungicide
- Hand sprayer
- Work gloves
- Safety goggles
- Ventilator mask
- Long-sleeved clothing
- Horticultural oil
- Insecticidal soap
Warning
- When spraying trees with herbicides, pesticides and insecticidal soap, wear proper safety gear. Launder all clothing and shower immediately afterward.
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About the Author
A writer with a Bachelor of Science in English and secondary education, but also an interest in all things beautiful, Melissa J. Bell has handed out beauty and fashion advice since she could talk -- and for the last six years, write for online publications like Daily Glow and SheBudgets.
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