Black aphids, like black squirrels, are striking in contrast to their leafy green backgrounds. But like squirrels, aphids are sometimes a nuisance, feeding on something we don’t want them to eat or damage. The black bean aphid, seen here on Euonymus, is fun to see but it can cause injury to the plant when its population is high.
Various instars of the black bean aphid on one of its winter hosts, Euonymus.
It does have a pretty interesting life cycle. Like many aphids, the black bean aphid has both a winter host and a summer host. It overwinters on Euonymus or Viburnum in the egg stage. As temperatures start to warm in the spring, the eggs hatch and there are 2-3 generations of wingless, asexual females (produce young without mating) before winged asexual females appear. These winged females migrate to the summer hosts. Summer hosts of the black bean aphid include beans, corn, sugarbeets, lambsquarters, and pigweed. Multiple generations occur on these hosts and populations can build up very rapidly, consisting of wingless, asexual females. In the fall, winged asexual females and winged sexual males return to the winter host and have one generation of sexual females. Mating occurs and eggs are laid for overwintering.
This winged asexual female will soon migrate from the Euonymus to a summer host where she will begin feeding and laying eggs.
The most effective management strategies for controlling aphids include preventing the population from increasing to damaging levels by monitoring, encouraging natural enemies, and the use of non-toxic or least toxic sprays. Monitor host plants beginning early in the season. Check the undersides of the leaves and hidden places on the plants. A sticky substance on the plant may indicate the presence of aphids. This is honeydew, excreted by aphids and other insects with piercing and sucking mouth parts. Sooty mold fungi may grow on this and cover surfaces with a black coating. Ants also like honeydew and may be found as well.
If aphids are present, they can be dislodged using a strong spray of water (not strong enough to injure the plant!). Encourage natural enemies by avoiding the use of chemical insecticides and by providing flowers to attract the adults of parasitoids.
Least toxic sprays include insecticidal soaps, horticultural oils and neem products. Test these on a small area of the plant to make sure plant injury does not occur. Plant injury is most likely when temperatures exceed 85°F.
J Allen
Uconnladybug's Blog 
May 18, 2012 at 1:03 am
Aren’t Euonymous invasive in Connecticut? If so, maybe the most effective aphid control is to remove the plant.
May 19, 2012 at 12:11 am
Hello Dave,
All Euonymus species are not invasive in Connecticut and not the one in the photo. Burning bush (Euonymus atlatus) is the one on the CT Invasive Plant List. Here is a Clemson University link to an article on the many species of Euonymus. Invasive plants are non-native plants that are disruptive in a way that causes environmental or economic harm, or harm to human health. In Connecticut, the Connecticut Invasive Plants Council has developed a list of non-native plants that cause (or have the potential to cause) environmental harm in minimally-managed areas.
In minimally-managed areas, invasive plants crowd out native plants. The presence of invasive plants alters the way plants, animals, soil, and water interact within native ecosystems, often causing harm to other species in addition to the plants that have been crowded out.
Here is a link to CT Invasive Plant List. http://www.hort.uconn.edu/cipwg/pdfs/CTInvasivePlantList2011-ScientificName.pdf
May 19, 2012 at 3:00 am
My mistake, sorry. I have been trying to get rid of Burning Bush on my property, so I’m sensitive right now. Looking at both your Plant Database and the Clemson link you provided, your web site seems more comprehensive in some ways. You list 2 Euonymus species as invasive (Euonymus europeaus & Euonymus fortunei) in addition to Euonymus atlatus.