Willow Flea Weevil Infestation: Identification and Systemic Control

Tiny Black Bugs with Orange Legs = Willow Flea Weevil

Rhynchaenus rufipes—adults 0.1″ long, black, orange legs. Larvae mine leaves. Two-four generations/year cause progressive browning, defoliation.

Life Cycle & Damage

• Adults emerge May, feed on new leaves (shot holes).
• Eggs in leaf punctures June → larvae mine leaves (blotch mines).
• Adults emerge Aug, feed again → overwinter in soil/bark.
• Repeated defoliation weakens tree over years.

Control Options

Foliar Sprays (If Tree Sprayable)

• Timing critical: Early June (1-11) after leaves flatten.
• Second spray early July (1-4) for new growth.
• Registered: bifenthrin, chlorpyrifos, pyrethrin.

Systemic Soil Drench (Best for Large Willows)

• Imidacloprid (Bayer Advanced Tree & Shrub) applied to root zone.
• Translocates to foliage → kills adults/larvae as they feed.
• 2-3 weeks to canopy; protects all generations for season.
• One application = year-long control.

Why Sevin Failed

Carbaryl (Sevin) has short residual (3-5 days). Weevil generations overlap; new adults emerge daily from surrounding areas. Systemic provides continuous protection.

Long-Term Outlook

• Willows tolerate weevils but repeated defoliation reduces vigor.
• Systemic treatment breaks the cycle.
• Healthy tree (water, mulch, moderate fertilizer) resists better.