Elm-pear woolly aphid

Taxonomy: The elm-pear woolly aphid (Schizoneura lanuginosum) is a member of the Hemiptera order and the Aphididae family. It is a highly specialized aphid species characterized by its distinct host-alternating lifecycle, requiring both elm and pear trees to complete its annual development cycle.

Host plants: The primary host for this pest is the elm tree, where it induces the formation of specific galls. During the summer months, the aphids migrate to their secondary host, the pear tree (Pyrus spp.), colonizing the roots and significantly impacting the vitality and root development of the trees.

Biology and lifecycle: The species overwinters as eggs in the crevices of elm bark. In the spring, the nymphs emerge and feed on leaves, triggering the growth of large, pouch-like galls. By mid-summer, winged migrants leave the elm to find the roots of nearby pear trees, where they establish colonies covered in white, woolly, wax-like secretions.

Damage and economic importance: The damage on elms is mostly cosmetic, characterized by large, disfiguring galls on leaves. However, on pear trees, the damage is severe as the aphids feed on the roots, leading to reduced nutrient uptake, stunted growth of the branches, chlorosis of the foliage, and, in severe infestations, the death of young saplings.

Control measures: Integrated pest management strategies are essential. Key practices include:

• Physical removal and destruction of elm galls before the migration period.
• Spatial isolation to prevent proximity between elm and pear orchards.
• Application of systemic insecticides directed at the root zone of affected pear trees to target subterranean colonies.