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Sooty Mold on Large Meyer Lemon: Scale Control for Big Bushes

The Problem

Large (8×8×8 ft) Meyer lemon bush. Black residue on fruit = sooty mold, growing on honeydew from scale insects (or whiteflies). Previous whitefly infestation supports this.

Confirm Scale

Inspect carefully: adults = 5 mm circular/oval flat bumps on leaves/stems; juveniles = mobile white tufts; mealybugs = white fluff at leaf-stem junctions.

Treatment for Large Plants

Insecticidal soaps sprayed thoroughly (both leaf sides).
Horticultural oils (dormant/Volck) — smother scale. Critical: Follow label exactly; temperature-sensitive; can damage foliage if misapplied.
Systemic insecticides (soil-applied) for season-long control.
Multiple applications over 4–8 weeks likely needed.

Local Expertise

Your garden center can recommend products and rates for your climate and tree size.

Plant Diseases: Meyer Lemon Tiny Black Fruit: Normal Abortion or Transplant Shock?; Meyer Lemon Sticky Leaves: Honeydew from Sap-Feeding Insects; Meyer Lemon Scale: Horticultural Oil Protocol; Webs on Indoor Meyer Lemon: Spider Mites, Scale, or Mealybugs?; Scale and Sooty Mold on Potted Meyer Lemon: Treatment and Prevention; Scale Insects on Meyer Lemon: Sticky Leaves, Brown Bumps, and How to Save Your Tree; Scale Insects and Ants on Meyer Lemon: Integrated Control for a Healthy Tree; Sticky 'Dirt' on Dwarf Lemon Leaves: Scale, Sooty Mold, and Protecting Your New Lime Tree; Comprehensive Scale Treatment for Ficus; Caring for a Container Meyer Lemon Tree: Pruning Blooms, Repotting, and Winter Protection

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