Sooty Mold on Mugo Pine: Treating the Underlying Insect Problem

Sooty Mold on Mugo Pine: Treating the Underlying Insect Problem

Blackened branches on one of two similarly situated mugo pines usually indicate sooty mold—a black fungus growing on honeydew excreted by sap-feeding insects like aphids, scale, or mealybugs. If the black coating wipes off with a wet finger, it's sooty mold.

Control Strategy

1. Identify the insect culprit by examining needles and stems for small, immobile bumps (scale) or clusters of soft-bodied insects (aphids).
2. Apply an appropriate insecticide: horticultural oil for scale, insecticidal soap or neem oil for aphids, or a systemic like imidacloprid for season-long control.
3. Once insects are suppressed, sooty mold will weather away naturally.

Consult your local nursery for product recommendations suited to your area and the specific pest.