A pest that causes damage by feeding on spruce needles
Spruce spider mites feed on the needles of conifer trees, causing a bronze or rust coloration. The needles may drop off the tree. Spider mites can be very destructive to evergreens.
Infested trees require chemical treatment for control
Spruce and arborvitae are most susceptible to spider mites. The infested tree or shrub will require a topical or systemic treatment for control of mites. Although mites are very small, their populations build up quickly. When extensive damage is observed, it may be too late to treat for the season. If treatment is timed correctly, mites are easily controlled and rarely life threatening.
What to look for
• Small yellow or tan dots on needles.
• Strands of webbing.
• To determine if you have spider mites, shake a branch over a white piece of paper and look for crawling mites. They will be about the size of ground pepper particles. Treatment may be warranted if you find more than 10 mites per branch.
• Mites remain on the bark and needles of the host plant through winter.
• Eggs hatch in April and May.
• The young mites feed on needles formed the previous year.
• Mites are most active during the cool seasons:
– April and May.
– September and October.
Treatment and Prevention
• Use fertilizer that is low in nitrogen.
• Make sure watering is adequate.
• Trees planted too close together are more susceptible.
• Shaded trees are more susceptible.
• Place flowering plants in vicinity – they will provide increased nectar sources for predators.
• Treatment timelines are dependent upon your tree, landscape, insect infestation levels, time of season, and available treatment options.