Viburnum Leaf Spots and Stem Lesions: Check for Scale First

Snowball viburnum has white/gray spots on upper leaves, then leaves blacken, curl, fall. Same spots on branches. New growth starts clean then repeats. What is this?

Primary Suspect: Scale Insects

• Oval, cottony-covered bumps on stems/leaves
• Don't move when feeding
• Scrape off with fingernail
• Cause yellowing, dieback, sooty mold

Secondary: Powdery Mildew

• White powder on leaves (wipes off)
• Doesn't affect woody stems
• Favored by shade, humidity

Next Step

Inspect closely for scale. If found → systemic imidacloprid soil drench. If not → fungicide for powdery mildew (propiconazole, myclobutanil, sulfur).