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Cottonwood Leaf Beetle

Characteristics:

  • Eggs: Bright yellow eggs hatch in 2 weeks.
  • Larvae: Mature larvae are blackish with two white spots on each side of each segment. Larvae can be up to 12 millimetres long. If disturbed, the larvae will emit a pungent odour. After feeding for 2 to 3 weeks, larvae pupate.
  • Pupa: Pupa hang head down from leaves, bark, weeds, or grasses under the host tree.
  • Adults: Beetles are 8 millimetres long, have a moderately convex body shape which is slightly oval. Their heads are black; their bodies are black with yellow or red edges; and their wings are yellow with several elongated dark spots. In the spring, they begin feeding on the growing tips of leaves. After summer, adults over winter under bark, litter, or other garden debris.

Identifying infestations:

  • Stunted and deformed trees: Trees cannot grow properly since larvae and adults eat the growing tip of trees.
  • Skeletonized leaves with intact veins: Again, larvae eat leaves but do not eat the midrib or veins.

IPM Toolkit:

  • Preventive tools:
    • Cold winters with little or no snow cover can cause many adult cottonwood leaf beetles to die.
  • Physical tools:
    • Wash larvae from trees with a high-pressure hose.
  • Biological tools:
    • Ladybird beetles feed on eggs and larvae.
  • Least toxic chemical tools: Not applicable