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Scale

Characteristics:

  • Eggs: Females give birth to either live mobile young (crawlers) or eggs under their scale, depending on the species. Outdoors, most scale insects overwinter as eggs.
  • Larvae (Crawlers): Crawlers travel to find a suitable spot on a plant. Once found, the crawler begins to feed. They then molt and form a small shell or waxy covering (known as a scale). The pest becomes immobile at this point.
  • Adults: Adults appear in mid to late June. Males emerge as delicate, two winged insects that do not eat; they mate and die. Adult females remain feeding under their scale.

Identifying infestations:

  • Weakened plants: Since scale insects suck plant sap which can weaken or damage the plant. If an infestation is severe, the plant may die.
  • Bumps on stems and leaves: Scale appears as a bump on stems or leaves. The protective shell can very small or quite large. The presence of numerous shells may not indicate a severe infestation since old, dead shells take years to fall off. The population is growing if shells appear on the plant’s new growth each year.

IPM Toolkit:

  • Preventive tools:
    • Follow a regular watering, fertilizing, and pruning schedule to keep your plants as healthy as possible to resist attack.
  • Physical tools:
    • Dislodge or kill crawlers with a strong blast of water.
    • Remove crawlers and adults by running your gloved hand along infested branches and stems to dislodge the insects.
  • Biological tools:
    • Lady bird beetles and parasitic wasps eat scale insects.
  • Least toxic chemical tools:
    • Apply Dormant Oil in the spring before leaf buds break open to control crawlers.
    • Control crawler populations with an insecticidal soap. Apply according to label directions.