Acacia scale

The Acacia scale (Eulecanium nocivum) is a destructive sucking insect belonging to the order Hemiptera and the family Coccidae. It is a significant pest in orchards and parks, often overlooked until the damage becomes severe enough to threaten the health of the host plants.

This pest is highly polyphagous, attacking a wide range of woody plants. While it commonly infests Robinia pseudoacacia, it causes substantial economic damage to various fruit crops including apples, pears, plums, and peaches. Its ability to infest both ornamental and fruit-bearing trees makes it difficult to eradicate completely.

The life cycle typically includes one generation per year. The insect overwinter as second-instar nymphs on the bark of host plants. With the return of spring, nymphs migrate to the leaves and twigs to complete their development. By early summer, females develop a distinct, hardened, brown shell beneath which they deposit hundreds of eggs.

Direct damage occurs when the insects extract sap from the plant tissues, leading to stunted growth and reduced vigor. Furthermore, the secretion of honeydew encourages the growth of sooty mold, which blocks sunlight from leaves and interferes with essential photosynthetic processes. In heavy infestations, trees may suffer from branch dieback and decreased cold hardiness.

Control strategies require a well-timed approach. Dormant oil applications in late winter are highly effective in targeting overwintering nymphs. During the summer, systemic insecticides should be applied precisely when the crawlers emerge, as this is the most vulnerable stage in their life cycle. Regular monitoring and removal of heavily infested wood are essential components of sustainable orchard management.