Oak giant aphid

Systematic position: The oak giant aphid (Stomaphis quercus) is a member of the Hemiptera order and the Aphididae family. It is recognized as one of the largest aphid species in Europe, distinguished by a remarkably long proboscis, which it uses to tap into the phloem of oak tree bark, reaching deeper layers than most other aphid species.

Crops: This pest primarily affects oak trees (genus Quercus). It is particularly attracted to older trees with deep fissures in the bark, where the aphids can hide while feeding. The pest is predominantly found on the trunks and major limbs of its host plants rather than on the leaves.

Biology and life cycle: The species exhibits a complex life cycle characterized by seasonal transitions. Eggs overwinter in the crevices of the tree bark. In spring, stem mothers hatch, initiating several generations of wingless females. By autumn, sexual forms appear, leading to the deposition of overwintering eggs. The species is highly associated with ants, which protect the aphid colonies from predators in exchange for honeydew.

Character of damage: Damage is primarily caused by the extraction of large volumes of sap from the bark, which weakens the host tree. Furthermore, the excretion of significant amounts of honeydew promotes the growth of sooty mold, which covers the bark and impairs gas exchange. Heavy infestations often lead to crown dieback and increased vulnerability to secondary pests and fungal infections.

Control measures: Management of Stomaphis quercus is typically directed at nurseries and urban landscapes where trees are under higher stress. Effective control includes the application of systemic insecticides during the early spring when the fundatrices are active. Reducing ant activity on the tree trunks through the use of sticky barriers can also significantly limit the aphids' spread and success.