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Spidermites

Characteristics:

  • Eggs: Females lay their eggs on leaves and needles of plants. Some mites overwinter as eggs.
  • Adults: Mature adults are extremely tiny (0.4 mm in size) and have 8 legs.

Identifying infestations:

  • Yellowing leaves or needles: As mites eat, they destroy the chlorophyll-bearing cells as they suck the sap from the plant. Therefore, the plant’s leaves or needles may look yellowed, flecked, stippled, or bleached.
  • Tiny needle-like puncture marks: Tiny holes may appear on the leaf where mites feed.
  • Fine silk webs or dirty cotton masses: You may see webs between the needles on spruce and pine trees or webs that look like tiny mats of dirty cotton on the leaf surface.
  • Presence of mites: Shake or bump the leaves/needles of an infected branch held over a piece of paper. If there is an infestation, you should be able to see the mites on the piece of paper.

IPM Toolkit:

  • Preventive tools:
    • If growing conditions are wet and cool, spider mites will not reproduce as often. Spider mites multiply fastest under hot, dry conditions.
    • Follow a regular watering, fertilizing, and pruning schedule to keep your trees and plants as healthy as possible to resist attack.
  • Physical tools:
    • Dislodge mites by spraying plants with a cold jet of water on a regular basis.
  • Biological tools:
    • Carnivorous insects and predatory mites eat spider mites.
  • Least toxic chemical tools:
    • Use Dormant Oil or a 2% solution of horticultural oil in the spring according to label directions.
    • Frequently apply insecticidal soap on infested areas according to label directions.