European asparagus aphids

Description. The European asparagus aphid is a small blue-green to gray-green aphid about 0.06 inch (1.5 mm) in length. The aphid is often covered with a powdery wax. Unlike most aphids, the cornicles of European asparagus aphid are reduced to practically invisible openings on the abdomen. The cauda, a projection at the very rear tip of the abdomen, is relatively long compared with other aphid species and has sides that are nearly parallel. The antennae are short.
The wingless forms of the aphids like to feed where the needles of the fern attach to the petioles. Their small size and coloration make them difficult to spot even upon close examination. Winged forms often occur in very large numbers that may appear as a large cloud. The aphid overwinters as eggs deposited on the old fern or in cracks in the soil.
Damage. Damage from European asparagus aphid is primarily from a toxin that the aphids inject into the plant when feeding. The toxin causes shortened internodes on subsequent growth, resulting in a tufted appearance that is called bonsai growth. While other factors can cause a limited amount of this type of distorted growth, heavy European asparagus aphid infestations produce this distortion in great profusion. Heavy populations also produce massive amounts of honeydew that may lead to considerable ant activity.
Because asparagus is a perennial plant, the important damage is the impact of the European asparagus aphid feeding on the subsequent year's growth. The distorted growth is unable to adequately nourish the plant's crown and it will desiccate after 1 or 2 years feeding by this pest. The toxin may also cause a delay in bud break in spring followed by a profusion of small spears produced simultaneously. The impact is especially pronounced on newly established or weak plantings, and in seedling beds.