Plum fruit scale

The plum fruit scale (Sphaerolecanium prunastri) is a significant pest belonging to the Coccidae family within the order Hemiptera. This insect is named for the globular, spherical shape of the adult females, which often cluster on the bark of host trees, making them easily identifiable during dormant season inspections.

This pest primarily targets Rosaceae plants. It is particularly devastating to plum trees, though it also thrives on apricots, peaches, almonds, and sloe. When infestations go unchecked, the scale can rapidly cover twigs and branches, leading to a substantial decline in the tree's overall vigor and fruit production capacity.

The life cycle is univoltine, meaning there is only one generation per year. The insect overwinters in the second-instar larval stage, typically tucked away in bark crevices or at the base of buds. As the sap begins to rise in early spring, these larvae migrate to younger branches and begin feeding aggressively, maturing into adults by the onset of summer.

The damage caused by these insects is primarily due to nutrient loss from sap-sucking.

• Stunted growth of new shoots and general tree weakening.
• Premature leaf drop and significant reduction in fruit yield.
• Development of sooty mold on the honeydew secreted by the scales.
• Increased susceptibility to frost damage and secondary diseases.

Effective management requires a multi-faceted approach. Early spring dormant oil or insecticide applications are crucial to control the overwintering population before bud break. Later, during the crawler stage in early summer, systemic insecticides provide optimal control. Cultural practices, such as removing heavily infested branches and ensuring proper tree health through irrigation and pruning, are essential components of long-term integrated pest management.