The Asian woolly hackberry aphids seemed to be back with a vengeance this summer.
These aphids are the little white things you see floating around in the air. I see them around my house and even more around my office on Greene Street.
Aphid populations have been up and down each year since 2001, when they were everywhere. I had more than 100 calls to my office in three days! In 2006 they were pretty bad, too.
Most people mistakenly call them whiteflies, which can be common right now on gardenias and anything in the privet family.
As the name implies, these aphids are coming from hackberry (sometimes called sugarberry) trees. I don’t think they are feeding on any other species. If you find them on other plants, it is just because they have landed there.
Hackberry trees are not a desirable tree. Nobody ever plants one; we just inherit them when they are allowed to grow. Hackberries have light-gray bark with narrow, corky projecting ridges on the trunk. They are plentiful in the woods and on abandoned sites around town because they come up like weeds.
These aphids cause the same problems whiteflies do. They suck the juice out of the leaves and secrete sticky honeydew on them. The parasitic fungus, sooty mold, grows as a result. So you have a black sticky mess, not only on the hackberry trees, but also on any plant or item below it, including cars and patio furniture. Cars parked under the trees become quite a mess.
Hackberry aphids give live birth during most of the growing season when the leaves are present. Spring and summer adults are all reproductive females. In fall, winged males are produced, aphids mate and females lay eggs during winter on branch terminals. Eggs hatch in the spring after hackberries produce leaves. The insects have several generations per year, so they can become very abundant by late summer.
I suspect the population will continue to fluctuate from year to year. Many factors are involved, with one of the main ones being the predator-prey ratio. Ladybird beetles are well-known beneficial insects that eat these aphids.
The best option for control is to use a systemic insecticide that contains the active ingredient dinotefuran. It will provide a quick knockdown of these pests. It is sold under various trade names, including Safari and Ortho Tree and Shrub Insect Control. A commercial product is called Zylam.
Apply dinotefuran on the root system, and the tree takes up the insecticide. Dinotefuran will last about six weeks, which is probably all you need.
Another option would be a systemic insecticide with the active ingredient imidacloprid, which works slower but lasts about three to four months. Ideally, imidacloprid should be used earlier in the season, around July Fourth. Products containing imidacloprid include Bayer Tree and Shrub Insect Control, Amdro Tree and Shrub Care and Spectracide Tree and Shrub Insect Spray Concentrate. The commercial product is called Merit.
Since dinotefuran has become readily available and less expensive, you can wait until the aphids appear to determine whether treatment is needed.
Don’t overlook small hackberry trees or bushes, as they can come up everywhere near the hackberry tree. Cut them down or spray with a systemic insect spray. The aphids will not kill the tree. They are a nuisance because of the black sticky mess they create.
REACH SID MULLIS, THE DIRECTOR OF THE UNIVERSITY OF GEORGIA EXTENSION SERVICE OFFICE FOR RICHMOND COUNTY, AT (706) 821-2349 OR SMULLIS@UGA.EDU.