Scale Insects on Variegated Shrubs: Identification and Control Options

Raised white and brown spots on leaves and stems of variegated shrubs that don't move but rub off easily are characteristic of scale insects. With hundreds of scale species in the U.S., exact identification without magnification is difficult, but the management approach is similar for most armored and soft scales.

Confirming Scale

• Spots are slightly raised, round to oval, 1-3 mm.
• Colors vary: white, brown, gray, or black.
• Do not move when prodded; firmly attached.
• Rub off with thumb, often leaving a wet smear (soft scales) or dry wax (armored scales).
• May be concentrated on certain branches or leaf undersides.

Insecticide Options for Scale Control

Active Ingredient	Example Products	Timing/Remarks
Paraffinic oil (Horticultural oil)	SunSpray, Volck Oil	Dormant or growing season; smothers all stages
Insecticidal soap	Safer's Soap	Effective on crawlers; repeat weekly
Chlorpyrifos	Dursban	Restricted use; professional application
Carbaryl	Sevin	Broad-spectrum; harmful to bees
Acephate	Orthene	Systemic + contact; good for armored scale
Malathion	Malathion	Contact; apply at crawler hatch

Application Strategy

1. Timing is critical: Target the crawler stage (mobile nymphs) which emerges in spring/early summer. Use sticky tape on branches to monitor.
2. Two applications 10-14 days apart catch successive hatches.
3. Thorough coverage: Spray to runoff on all surfaces—stems, leaf undersides, branch crotches.
4. Check label: Verify the product is labeled for your specific host plant.

Alternative: Systemic Soil Drench

Imidacloprid (Bayer Advanced Tree & Shrub) applied to soil provides season-long control without spray drift concerns. Best applied in early spring before crawler emergence.

Regular monitoring and early intervention prevent scale populations from reaching damaging levels. Healthy, unstressed plants are also less susceptible to severe infestations.