Ash bark scale

The Ash bark scale (Pseudochermes fraxini) is a sap-sucking insect belonging to the order Hemiptera and the family Kermesidae. It is a specialized pest that exclusively targets trees of the genus Fraxinus, often causing significant physiological stress and reduced aesthetic value in urban and forest environments.

This pest primarily infests the bark of branches and the main trunk of the ash tree. Being a member of the scale insects, it remains sedentary during its adult stage. The presence of the insect is easily identified by the white, woolly or felt-like waxy secretions that cover the females, which accumulate on the bark surface throughout the growing season.

The life cycle is typically univoltine, meaning there is one generation per year. The insect overwinters as a first-instar nymph, typically tucked deep within the bark crevices. As temperatures rise in spring, these nymphs emerge, settle on the surface, and begin feeding. After maturation and mating, the females lay eggs under their protective wax covers, which serve as a nursery for the next generation.

The damage caused by the Ash bark scale is primarily due to nutrient depletion of the tree. Constant sap extraction results in chlorosis, stunted growth, and the dieback of small twigs. Furthermore, the honeydew produced by the insects provides an ideal substrate for the growth of sooty mold, which further interferes with the photosynthesis process and creates a unsightly black coating on the bark.

Management strategies focus on early detection and chemical intervention. During the dormant season, horticultural oils can be applied to smother the overwintering nymphs. During the spring, when the "crawlers" are active, contact or systemic insecticides are highly effective. Maintaining tree vigor through proper irrigation and soil management is essential to help the tree recover from infestations and prevent future attacks.