Scale Insects on Sunburst Locust: Identification and Control Options

What Are Scale Insects?

Scale insects are a diverse group of sap-feeding pests that attach themselves to branches and leaves. They come in three main types: soft-bodied, hard-bodied (armored), and waxy-covered. All feed by piercing plant tissue and sucking out juices, weakening the tree and causing dieback.

Life Cycle and Vulnerability

Scales have three stages: egg, nymph (crawler), and adult. Only the crawler stage is mobile. Once settled, adults remain fixed in place, protected by their covering. This makes timing critical—controls must target the crawler stage.

Signs of Infestation

• Sticky honeydew on leaves and branches
• Black sooty mold growing on honeydew
• Visible bumps on bark (the scales themselves)
• Branch dieback and stunted growth in heavy infestations

Control Strategies

Low populations: Natural predators like ladybugs often keep scales in check.

Moderate to heavy infestations:

• Insecticidal soaps and horticultural oils: Require thorough coverage; kill on contact. Repeat applications needed.
• Conventional insecticides: Longer residual but similar timing and coverage requirements. Check labels for plant sensitivity.
• Systemic insecticides (e.g., imidacloprid): Applied as a soil drench; absorbed by roots and ingested by feeding scales. Best applied weeks before crawler emergence.

When to Act

Monitor for crawler activity in spring (often coinciding with specific indicator plants blooming). Your local extension office can provide precise timing for eastern Wisconsin.