Locust Borer: Sawdust from Trees in Nevada

Question: Two locust trees shedding sawdust daily in Northern NV. Plants underneath covered. Boring insect suspected.

Answer: Locust Borer (Megacyllene robiniae)

Longhorned beetle (Cerambycidae). Larvae bore into heartwood, ejecting yellow sawdust in late summer.

Damage & Risk Factors

• Broken/dead limbs, weakened trees, excessive sprouts, tree death
• Low-vigor, damaged, drought-stressed trees most vulnerable
• Trees <6″ diameter most attacked; >8″ generally safe

Management

1. Cultural: Fertilize 10-10-10 at 1 lb/inch trunk diameter; water in well. Vigorous spring growth = high larval mortality (sap flow).
2. Chemical (if needed): Trunk/limb spray with Merit (imidacloprid) or borer-labeled insecticide. Thorough coverage required.

Key Insight

Healthy trees resist borers. Focus on vigor first; spray only if necessary.