Origin:
Believed to be native to South Africa, but now found throughout the world in mild climates where susceptible plants grow. It is a particular pest of olive trees, but also attacks oleander, citrus, and some other forest and landscape trees and shrubs.
Biology:
Late instar nymphs overwinter on the stems of host plants, with the female developing in the spring and begins egg production. From 150 to over 1000 eggs may be produced within the scale covering. A second generation may occur with adult females producing eggs in the fall. Nymphs in the crawler stage then appear in June and July. After 2 to 3 weeks the crawlers become sessile, feeding at one point and beginning to form the wax shell over themselves. There are 3 nymph stages prior to the adult stage.
Identification:
The color of the wax scale is light brown in the nymph stages, becoming increasingly darker until it is dark black in the adult stage. There is an impression on the top of the irregular shaped scale that forms the letter “H”, also present in other species of scale. However, the jet black color and the presence on olive trees help to distinguish this species.
Characteristicts Important to Control:
Small infestations of the scale may not warrant a control program. A great many natural predators and parasitic insects have been discovered or introduced to combat this scale, and these help to keep populations below a threshold level. One of the bigger problems is the copious production of honeydew, which drips onto surfaces below and attracts ants and other sweet-feeding insects. Dormant oil applications to foliage and stems help kill the overwintering scales, and applications of contact insecticides timed to the emergence of the exposed crawlers will effectively kill them.
.jpg)