The cycad scale is a tiny, orange, sap-sucking bug that lives under a white or translucent shelter (scale) it constructs from anal secretions to protect it from weather and enemies. The scales of females are less than 2 millimetres long and highly variable in form. They tend to be pear-shaped but can be circular, oblong, or irregular in shape when scales are crowded together. They often remained attached to the cycad surface, even after the bug has died. The scales of male are long and narrow and smaller. They have a grooved surface.
The underside of this frond shows a scatter of female scales alongside the much smaller males. Photo: John A. Davidson, Univ. Md, College Pk, Bugwood.org
This species is very difficult to distinguish from similar scales, and it is their dense white infestations that should be looked for, in combination with sick and dying cycads. They should be looked for on cultivated cycads, and on wild cycads growing near houses.
The sago palm (Cycas revoluta), more properly called the sago cycad, is often grown in Australian parks and gardens and is highly susceptible. Plants under early attack reveal their plight by first showing small yellow spots on the upper surface of their fronds. As the infestation progresses fronds turn yellowish then brown and dry.
This cycad has brown dessicated fronds, a withering green frond, and frond stalks densely coated in cycad scales. Photo: F.W. Howard, University of Florida, Bugwood.org
This cycad is dying from scale attack. Photo: Florida Division of Plant Industry, Bugwood.org
Those who aren’t familiar with cycads may confuse them with young palms, since both have fronds. The leathery leaves of cycads are much thicker and stiffer than those of palms. The trunks are very thick for the height of the plant. Many cycads, including sago palm, have fronds on which each leaflet ends in a spine. Its leaflets are rigid and only about 4 millimetres wide.
Sago palms can suffer dieback on the tips of their leaflets, which can turn whitish, but this looks very different from scale attack, which is not directed at leaf tips.
A female scale can be seen here beneath her semi-transparent cover. Beside her are two male scales. Photo: Jeffrey W Lotz, Florida Department of Agriculture and Consumer Services, Bugwood.org | CC BY 3.0