Adults: The adult aphids are pear-shaped and black-grey with white spots and a pair of red spikes on the rear end. They're under 0.5 cm. Nymphs: Smaller and paler grey.

Copious amounts of honeydew may be evident near the site aphids are present. Honeydew can encourage the growth of black mould, so this may be notable too. Ants will protect aphids from some garden predators. Healthy Willow plants will survive damage.

Diurnal

These aphids provide an abundance of food for wildlife active during autumn. Despite their large numbers, they don't seem to affect overall tree health. Healthy, established trees can withstand damage. Spiders, ladybugs, lacewing, and hoverfly larvae eat aphids. You can attract these to your garden by providing insect habitats. These include things like hanging baskets, climbing plants, shrubs & trees, or strips of wildflowers. If aphid colonies become too large and plants begin to suffer, give plants a spray of soapy water or jet them off with the garden hose.