Integrated Pest Management
Cottony Maple Scale
Pulvinaria innumerabilis
Immature cottony maple scales and egg mass (Raymond Gill, California Department of Agriculture and Food, Bugwood.org)
Cottony maple scale egg sacs (Eugene E. Nelson, Bugwood.org)
Cottony maple scale egg sacs (Inzelbeth, Wikimedia Commons)
Pest Description
- females: 1/8 inch; convex; pale to dark brown
- immatures: crawlers (mobile stage) ~ 3/64 inch, yellow orange; no wings
- immatures: nymphs: smaller, flattened and oval; translucent yellowish; found on leaves
- egg sacs: white/cottony; grow from under females
Host Plants, Diet & Damage
- most common on maple; many hosts
- feed on plant sap from leaves/twigs/small branches
- infestations produce unsightly cottony masses
- branch and twig dieback; early leaf drop
- honeydew production; sooty mold
Biology, Life Cycle & Damaging Life Stage
- overwinter as mated, 2nd instar nymphs on twigs and branches
- cottony egg masses grow in spring
- eggs hatch June through July
- crawlers settle on the undersides of leaves near the midrib or veins
- mating occurs in late summer
- mated females migrate to twigs and branches to overwinter
- one generation per year
- nymphs and adults are the damaging stages
IPM Recommendations
- Manage trees to improve or maintain health.
- Monitor scale populations on host plants.
- Apply an insecticide (carbamate; horticultural oil; insecticidal soap; organophosphate; pyrethroid) to coincide with scale crawler activity.
- Apply a systemic neonicitinoid in spring after leaves have expanded.
For more information, see our Soft Scales in Utah Landscapes fact sheet.