Cycad scale—Furchadaspis zamiae
This armored scale (family Diaspididae) primarily infests and damages cycads, or sago palms (Cycas and Zamia species), and less commonly bird of paradise.
Adult females and nymphs occur on fronds (or leaves of hosts other than cycads) and the rachises (stems). Mature females are 1/25 to 1/10 inch long, oval to oblong, and moderately to strongly convex. The cover is white with a yellow or whitish exuvia (attached skin of earlier nymphal stage) at one end. The scale's cover is commonly covered with fine, woolly threads of white wax. Beneath the cover the scale's body is yellow. Nymphs resemble small females. Males are unknown in this species.
Cycad scale resembles oleander scale. Both species occur on bird of paradise, cycads, and various other hosts, but oleander scale generally does not harm plants. Adult females of oleander scale are mostly tan or yellowish with a roundish cover. Males are common in oleander scale; males have translucent white covers through which the scale’s body is partly visible. Oleander scale females are normally flat on most hosts, but on the narrow, curled leaves of some cycads they are more convex like cycad scale. In comparison with cycad scale, oleander scale females are more roundish, yellowish or tan, and have the exuvia (somewhat raised, differently colored area) near the center of the cover, not near one end as with cycad scales.
Oleander scale generally can be ignored, while cycad scale when abundant warrants management action. If it is uncertain which species is infesting cycads, consider submitting samples to the local office of the county agricultural commissioner or UC Cooperative Extension for identification.
Cycad scale develops through three life stages: egg, nymph, and adult. Eggs hatch within the body of the adult female and emerge as crawlers (mobile first instars). Nymphs develop through two, increasingly larger immature stages before maturing into adults. There are about two generations per year.
Cycad scale sucks and feeds on the fronds or leaves and rachis or stems of hosts. On bird of paradise and cycads, it causes severe yellow spotting or mottling of foliage. When abundant, cycad scale stunts the growth of cycads, which are expensive and generally slow-growing plants. Prolonged high populations can cause premature death of cycads.
Other hosts of cycad scale include Aralia, Cussonia, Maytenus, Musa, Rhus, Thevetia, Trachycarpus, and Strelitzia species; however the scale generally does not significantly damage these plants. See ScaleNet from the U.S. Department of Agriculture for a complete list of hosts and references for more information.
When the scale is abundant, control is warranted. Infested fronds and rachis can be thoroughly sprayed with horticultural oil during the dormant season or when monitoring indicates that crawlers are active in the late winter or spring. See the section "Monitoring" in Pest Notes: Scales for how to time applications by monitoring crawlers using sticky tape traps wrapped around a scale-infested portion of each of several rachises of cycad.
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.
Yellow spotting of fronds from feeding by cycad scale.
Cycad scale nymphs and adult females.
Cycad scale nymphs (left) and adult female.