Elm-currant aphid

The elm-currant aphid (Eriosoma ulmi) is an insect belonging to the order Hemiptera and the family Pemphigidae. This pest is known for its host-alternating life cycle, which requires two distinct plant species to complete its biological development throughout the year.

The primary hosts of this aphid are various species of elm (Ulmus), which support the population in spring and autumn, while the secondary hosts are shrubs of the genus Ribes, specifically currants, where the aphids reside during the summer months.

The life cycle begins with eggs overwintering on elm bark. In spring, stem mothers hatch and induce the formation of leaf curls or galls on elm foliage. Later, winged offspring migrate to the roots of currant bushes, where they feed on sap and produce several successive generations underground.

The damage to elms is characterized by stunted, deformed leaves curled into galls, which significantly reduces the tree's aesthetic appeal. On currants, the damage is more insidious, as the aphids colonize the root system, causing the plant to weaken, lose vigor, and exhibit reduced tolerance to environmental stress.

Effective management and control strategies include:

• Application of contact insecticides on elm trees in early spring before the buds open.
• Systemic insecticide soil drenching for currant bushes to target root-feeding aphid colonies.
• Removal and disposal of curled elm leaves before the winged aphids migrate.
• Maintaining optimal garden hygiene and ensuring strong plant health through proper fertilization.

Managing the elm-currant aphid requires vigilance, as the subterranean nature of the pest on currants often masks the severity of the infestation. Integrated pest management, focusing on the primary host (elm), is the most successful approach to reducing future pressure on berry crops.