Aphids on Blueberry Bush — How to Identify and Treat Them

Blueberries are hosts to several aphid species, most commonly the blueberry aphid (Illinoia pepperi) and the green peach aphid, both of which colonise the soft new shoot growth and the undersides of young leaves. A light aphid presence is tolerable and quickly dealt with by natural predators. A heavy infestation — dense clusters on every growing tip, with curled leaves and a sticky residue coating the stems below — weakens the plant and, more importantly, creates a serious risk of virus transmission.

Identifying the problem

Look for clusters of small, soft-bodied insects — pale green, yellowish or pinkish — on the undersides of young leaves and on the growing shoot tips. Affected leaves curl downward and inward around the colony. Below the colony you will typically find sticky honeydew on the stems and older leaves; black sooty mould often follows, growing on the honeydew deposits. On new growth, aphid feeding causes stunted, distorted shoot tips. The presence of ants moving up and down the stems is a reliable sign that aphids are active — ants farm aphids for honeydew and will actively protect them from natural predators.

Natural predators and waiting

Ladybirds, lacewings and hoverfly larvae are voracious aphid predators and will often clear an infestation within one to two weeks if left undisturbed. If the infestation appeared recently and the leaves are not yet heavily distorted, waiting and encouraging these predators is a reasonable first response. Avoid broad-spectrum insecticides entirely during flowering, as these will kill the bumblebees on which blueberry pollination depends.

Physical removal and water jets

For moderate infestations, a strong jet of water directed at the colonies on the underside of leaves removes most aphids. They cannot climb back up easily and most will desiccate or be eaten by predators. Repeat two or three times over a week. Pinching out the most heavily infested shoot tips removes the colony concentrations before they spread. Manage ants using a sticky barrier band around the main stem bases, which prevents them from climbing to protect the aphid colonies from predators.

Insecticidal soap

Where infestation is severe, insecticidal soap (potassium fatty acids) applied to the undersides of leaves is effective and has minimal impact on beneficial insects when applied in the evening after pollinators have left the plant. Do not apply any spray when flowers are open. Neem oil is similarly effective and acts as a deterrent as well as a contact treatment.