

Black soot left / Aphids Right
Are your plants looking like you have a coal mine right next to you? If so, read on. This summer I came across something I hadn’t seen before. I first spotted it on some 1st year small trees, then on a crape myrtle and then on some photinias. In addition to this black soot, there were some white/light green little egg looking things that covered some of the new growth. Puzzled, I did some quick research and discovered the source of this mystery. The culprit, aphids. I had read about aphids and new they existed but had no clue they caused this black sooty stuff on plants. As it turns out, aphids suck on the new growth to extract the plant juices. In turn, they secrete this stuff called “honeydew” which then molds (black stuff that you see). In addition to the black stuff, you may also notice that a lot of the new growth is deformed.
The incredible thing is that though the aphids are pretty small, the black stuff covers the entire plant! Also, if you look at the ground, you will find that it completely covers that as well. So it would seem that aphids are quite the voracious eaters!
The good news is that aphids are pretty easy to get rid of with either commercial pesticides or home remedies. Below are some suggestions depending on severity and/or style of gardening:
Severe Infestation
A severe infestation will probably require spraying. Just about any commercial systemic pesticide will do the trick. I used one called Sevin which works great on aphids and other pests. I like this option because it provides all around protection and one application is enough to do the trick for a while. Another alternative is insecticidal soap. It’s safer than spraying but this will only work on aphids and other soft bodied pests. You can find either at your local Home Depot or the like.
Medium Infestations or Organic Gardening
If you are an organic gardener or your infestation is medium, then you can simply mix some dish soap and water then spray the effected regions of the plant. The soap strips the wax covering the aphid’s body so a few sprayings may be needed to do the trick. Another home remedy is to mix some cooking oil along with your dish soap. I would try that as a last resort on more severe infestations and it should not be used on hot sunny days or on plants that get direct sun as the oil will cause sun damage on the foliage (may kill your plant).
Mild Infestations
For really mild infestations or at the first signs of aphids, simply knock them off with a stream of water from a garden hose nozzle. You can also use a manual approach and simply crush the little suckers with your finders (they pop very easily but watch out for PETA! =-). The downside to these methods is that you may miss some and they will quickly come back. So constant vigilance is required if this is your preferred method.
The bad news is that regardless of what you use, the black stuff/mold will remain on the foliage. You will have to clean that off manually leaf by leaf which is impossible unless you have a small plant. Of course you can leave it since it will not really hurt the plant. Just be vigilant the following year and eliminate the aphids as soon as you see them or use a preventive spray of systemic pesticide early in the year (if you don’t mind spraying). I am not sure on what causes aphids. My only theory is an unusually wet growing season which we had this year since I have not seen them during dryer seasons.