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Aspen Dripping Sap: Aphids, Not Tree Disease

Sticky Mist Under Aspens at 7,000 Ft

The "sap" dripping from healthy aspens is honeydew from aphid colonies. Aphids suck phloem sap and excrete sugar-rich droplets that coat leaves and surfaces below.

Management

Late-season infestations (leaves turning soon) don't warrant treatment. Next spring, if aphids return, apply a soil systemic (imidacloprid) at bud break for season-long control. Natural predators (lady beetles, lacewings) often crash populations naturally.

Trees: Aphids on Aspen: Honeydew, Sooty Mold, and Organic Management; Sudden Aspen Decline: Understanding Aspen Die-Off; Controlling Aspen Suckers in the Landscape; Managing Aspen Root Suckers Without Chemicals; Managing Aspen Suckers: Keep the Best, Remove the Rest; Identifying and Treating Scale on Aspen Trees; Aspen Trees Slow to Leaf Out at High Elevation: Patience Is Key; Pine Sap Function: Natural Wound Defense; Aspen Leaf Spots and Honeydew: Aphid Infestation; Propagating Aspen Trees: Nursery Methods and Invasiveness

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