A shout-out to Steven Frank, entomologist with the N.C. Cooperative Extension, for good garden advice.
In the current issue of North Carolina Pest News, Frank reports that crape myrtle aphids, one of the plant’s most common pests, are showing up in increasing numbers:
“Small populations are present in Raleigh and have been building over the past couple of weeks. Feedings by these aphids result in leaf yellowing and distortion, leaf drop and honeydew deposits, which of course lead to sooty mold.”
So, grab the strongest chemical off the shelf and spray now, right?
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Not so fast, Frank cautions.
“Crape myrtle aphids are generally kept in check by natural enemies,” he reports in Pest News. “When scouting for them, I often find almost as many lacewing eggs, ladybug larvae and other predators as aphids.”
The crape myrtle aphid attacks only crape myrtles. It is of Asian origin, like the crape myrtle tree itself. Crape myrtle aphids are tiny, only about a 16th of an inch long. They feed by sticking their mouthparts into a plant and sucking out the sugar-rich sap, like a teenager slurping down a frappuccino.
If the aphid infestation gets heavy, the plant can show obvious distress, such as drooping leaves and yellow spots. Worse from the standpoint of looks, the sticky waste given off by the aphids, called honeydew, spawns unsightly black mold.
In home landscapes, however, the best strategy may be to avoid toxic sprays. As Frank points out in a detailed N.C. State University fact sheet:
“Conserving beneficial insects is not just an environmentally responsible thing to do. It can improve control of pests such as aphids. Remember, an insecticide application will never kill every individual of a pest population. It is the job of natural enemies to clean up after and between insecticide applications.
“Otherwise, a few aphids that escape an insecticide application can rapidly reach damaging levels. Natural enemies of crape myrtle aphids include lady beetles and their larvae, green lacewings and their larvae, hover fly maggots, parasitic wasps and entomophagous fungi.
“Pay attention to the presence of these natural enemies when scouting, and you may be able to skip an insecticide application.”
Frank also lists pesticides for control of severe outbreaks that do less damage to beneficials, including two “organic” options, horticultural oil and insecticidal soap. He suggests checking a Clemson University list of crape myrtle varieties that naturally resist aphids, including Southern Living Magazine favorites “Natchez” (white flowers), “Osage” (light pink flowers, a smaller tree) and “Miami” (rose-colored flowers).
David Goforth, N.C. Cooperative Extension horticulture agent in Cabarrus County, shares the monthly NCSU pest report with his Master Gardener volunteers. Goforth reminds gardeners that pest and beneficial populations are linked, like prey and predators in natural ecosystems – the number of lions is based on the number of wildebeests and zebras.
Tolerating a reasonable number of pests, such as aphids, until natural systems restore balance is much more sustainable and sensible – and much less expensive and damaging – than a zero-tolerance policy based on heavy pesticide spraying.
If watching aphids suck your plants bothers you as much as mosquitos biting your neck at a summer picnic, there is another tried-and-true trick for aphids: Get out the hose and wash them off with a strong stream of water. This disrupts aphid feeding and the mold and other problems that go with it.
Speaking of the hose, it has other potential pest control applications.
In Autumnwood, a friendly neighborhood near UNC Charlotte known for its natural landscapes along Toby Creek, a conflict has arisen between a koi fancier and her cat-loving neighbor two doors down. Call them Ms. Pescado and Ms. Gato.
Pescado’s expensive koi, a type of colorful Asian carp, have been disappearing from her backyard pond. Sure that Gato’s tomcat was to blame, Pescado marched over to Gato’s house and threatened to eliminate the cat if it went anywhere near the fish pond.
In Charlotte and Mecklenburg County, that would not be wise. Pescado might get in trouble, since no local laws ban roaming cats if they have a collar and license.
Besides, the cat is probably not the culprit. Autumnwood’s sizable and bold raccoon population is much more likely to be dining on the koi.
If Pescado wants to discourage the cat, however, a discreet blast or two with the hose can send a clear message, without an unpleasant and unnecessary confrontation with her neighbor.