Calico Scale

Calico Scale

Identification: Eulecanium cerasorum — a soft scale (family Coccidae), 4–6 mm, with a hard, glossy brown cover marked by a white and black blotchy pattern that gives it the "calico" name. The distinctive patterned surface makes it one of the more identifiable soft scales in Middle Tennessee. Infests a broad range of shade trees and ornamentals including honey locust (Gleditsia triacanthos), euonymus, hackberry, dogwood, and various maples.

Life cycle: One generation per year. Overwinters as second-instar nymphs on bark of twigs and small branches. Nymphs resume feeding in early spring; females mature, swell noticeably, and produce crawlers from May through June. Crawlers settle on leaves through summer and return to bark in late summer. Mature calico-patterned females in May just before egg laying are the most noticeable life stage.

Damage signs: Heavy honeydew production on host trees, sooty mold on foliage and surfaces beneath infested trees, and branch dieback on small-diameter limbs. Honey locust in urban landscapes in Middle Tennessee — a commonly planted street and parking-lot tree — can sustain repeated infestations that progressively thin the canopy. Nymph feeding in spring causes chlorosis and reduces shoot elongation.

Treatment window: At crawler emergence in May–June for contact treatments. Dormant oil in late February–March reduces the overwintering nymph population. Systemic applications are most effective when applied in early spring before adult females mature.

UT-recommended approach: Dormant horticultural oil as the primary intervention on manageable-sized trees. Systemic imidacloprid soil drench in early spring for recurring infestations on large trees. Crawler-stage insecticidal soap in May–June addresses the remaining population. Monitor honey locust along driveways and parking areas in the Columbia, TN area annually — populations on heat-stressed urban trees tend to be most severe.