Walnut aphid

Walnut aphids are easily distinguishable from dusky-veined aphids. They are much smaller and are typically found scattered on the lower side of leaves. Dusky-veined aphids feed in rows along the midvein on the upper leaf surface. During spring and summer, adult females are commonly winged, and their wings have distinctive dusky markings along the veins. Nymphs of the dusky-veined aphid have dark, banded spots on the back. These spots are much less pronounced or absent on the nymphs of the walnut aphid. In the last few years, a white form (morph) of the walnut aphid has been found in the Sacramento Valley. Populations of the white morph build later in the season than normal-colored ones.