Oleander scale—Aspidiotus nerii
Also called ivy scale or white scale, this armored scale (family Diaspididae) may be the most common scale insect in California. While unsightly when abundant it rarely, if ever, causes serious harm to plants.
Oleander scale’s cover is nearly circular, flattened, and found on bark, foliage, and fruit. Female covers are tan to yellowish and at maturity 1/16 to 1/12 inch in diameter. The cover of immature males is smaller and translucent white. Through the cover, the male body is partly visible. The easily overlooked adult male is about 1/25 inch long and has a delicate, orangish body with long antennae and one pair of wings.
Oleander scale resembles greedy scale and latania scale, but their covers are more globular or raised. The darker, raised bump (exuvia, cover of the earlier nymphal stage) of oleander scale is commonly near the scale's center; the exuvia of greedy and latania scales is near the side of their covers. It is difficult to reliably separate these species in the field, but this generally is not of practical importance as these three species generally do not damage hosts or warrant management.
Note that cycad scale is another look-alike species and it is a serious pest of cycads, or sago palms (Cycas and Zamia species). In comparison with oleander scale, cycad scale on sago palms is lighter colored, more convex, and commonly oblong. Submit samples to an expert with the county agricultural commissioner or UC Cooperative Extension for identification if it is uncertain what species is infesting cycads. Greedy scale, latania scale, and oleander scale generally can be ignored, while cycad scale when abundant on cycads warrants management action.
Armored scales develop through three life stages: egg, nymph, and adult. Oleander scale overwinters as mature females, which produce crawlers (mobile first instars) beginning in late winter. Female nymphs develop through two, increasingly larger immature stages and males develop through four immature stages before maturing into adults. There are two to four generations per year in California.
The scale sucks and feeds mostly on leaves, but occasionally also on stems. The pale scale covers can give foliage a crusty appearance, reducing aesthetic appearance. Otherwise, oleander scale generally does not damage hosts or threaten plant health.
Oleander scale can infest over 300 genera of plants as listed at ScaleNet from the U.S. Department of Agriculture. The most common hosts of oleander scale include aucuba, cycad or sago palm, ivy, oleander, and olive. Its many other hosts include acacia, bay, boxwood, fruit trees, holly, laurel, magnolia, manzanita, maple, mulberry, pepper tree, redbud, rose, yew, and yucca.
No control is needed to protect plant health. If unsightly, prune out heavily infested branches as long as this does not entail extensive removal of a plants' leaves and limbs.
Numerous parasitic wasps and predatory insects feed on oleander scale as listed at ScaleNet. Predators include the black lady beetle (Rhyzobius lophanthae), green lacewings, minute pirate bugs, and twice-stabbed lady beetle. To conserve (preserve) natural enemies and improve biological control, control ants, reduce dustiness (e.g., periodically hose off shrubs), and avoid the use of persistent, broad-spectrum insecticides and miticides. See Protecting Natural Enemies and Pollinators for more information.
Where intolerable, horticultural or narrow-range oil can be sprayed to thoroughly cover infested parts during the dormant season or when monitoring indicates that crawlers are active in late winter or spring. See the section "Monitoring" in Pest Notes: Scales for how to effectively time applications by monitoring scale crawlers using sticky tape traps.
Adapted from Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM) and The Scale Insects of California Part 3: The Armored Scales (Homoptera: Diaspididae), California Department of Food and Agriculture.
Oleander scales on ivy.
Female (tan) and male (white) oleander scales.
Adult male oleander scale.