Woolly alder aphid, Paraprociphilus tesselatus, is active at The Morton Arboretum in Chicago. This species is not a major plant-feeding pest. However, these aphids cover themselves with white, fluffy wax that resembles lint, and this is what is most noticeable. Woolly alder aphid requires two hosts to complete its life cycle: alder (Alnus spp.) and silver maple (Acer saccarinum).
Eggs are deposited in the fall into the bark of maples. The eggs hatch in spring into immatures, or young, that migrate to the underside of leaves, and then they settle to feed at the leaf midvein. All the young aphids are female (stem mothers), which can reproduce asexually (without mating). The feeding by the young aphids causes leaves to curl upward, creating a protective habitat, or cover. Eventually, the young develop into migrants that fly to alder trees. The winged migrants are large (about 10 mm from wingtip to wingtip). The aphids on the alder trees start a new generation. In fact, several generations may develop on an alder tree. Aphids, feeding excessively on plant tissues, produce large quantities of honeydew. In addition, the aphids cover themselves with white, fluffy wax filaments. In the fall, they migrate back to silver maples to lay eggs.
The woolly alder aphid is not a plant-injurious pest. It is primarily a nuisance due to the amount of white, woolly threads that accumulate on the ground and the migrating aphids that seem to float through the air. As a result, insecticide applications are generally not recommended, mainly because they may kill natural enemies of the aphid. Woolly alder aphid is susceptible to a number of predators, including lacewings and lady beetles. Spraying plants with a hard stream of water greatly reduces aphid numbers and minimizes any long-term effects on natural enemy populations.