Wooly Aphids on Hackberry Trees

gillnurseryProblem Solving10 Comments

Over the past few weeks there have been numerous inquiries about whiteflies on trees. However, these insects are not whiteflies. They are actually a large infestation of Asian wooly aphids. Wooly aphids are small white insects that fall off hackberry trees and appear to float in the air. They suck the sap out of the leaves and secrete a sticky residue called honeydew. As a result, a black mold, known as sooty mold, covers the leaves, stems and possibly the bark of the tree. This black sticky substance covers the hackberry tree, and it can cover any plant or object underneath it. When I see black soot on certain plants that are not prone to any specific insect, I always ask, “what’s above this plant”? I will usually find a hackberry tree nearby. It does not have to be directly above, just nearby. This black soot gets on vehicles, lawn furniture and anything else in the fallout zone.

To control the problem, insecticides are not always necessary, but they may be justified when honeydew and sooty mold become intolerable. If the tree is small enough to spray, you can use spinosad. For larger hackberry trees, it may not be feasible to spray the leaves with an insecticide for control. It is possible to use a systemic insecticide such as Bayer Tree and Shrub Protect and Feed applied as a root drench around the base of the tree. Systemic chemicals take several weeks to move from the roots into the leaves. Systemic insecticides should be used in the spring shortly after the leaves emerge and again in late summer for longer control. I usually treat my neighbors tree in April since wooly aphids appear every year in June to July. That way I am sure the chemical is still at its optimal control strength.

deannaAnother option for control is to remove the host tree from the landscape. This will immediately eliminate the problem since these aphids only damage hackberry trees. The down side to systemic insecticides and tree removal is the hackberry is a wonderful tree for birds with its berries. It is also the host plant for the Snout butterfly. Most importantly, now you have the information needed to make the best decision for you, the tree and the environment.


10 Comments on “Wooly Aphids on Hackberry Trees”

  1. I purchased a home in Sacramento CA and I believe the large tree in my front yard is a hackberry. I was shocked to find the entire tree oozing a sticky substance all over my driveway as well as the sidewalk and street.
    It is as you described, white aphids covering the leaves of the entire tree, causing the tree to ooze a dark sticky substance. The tree is too large to spray. How dangerous are the root chemicals and how long does the infestation last if gone untreated. Will the aphids cause damage to the tree?
    Thank you for your help.

  2. The infestation will last until the tree defoliates in fall/winter. The tree will not be seriously damaged but it does suffer an “energy deficit” due to the infestation which could be a factor if other “insults” are present. Since you are so close to leaf drop I would not treat.

  3. I have had these on my hackberry trees for several years & had no idea as to what they were, so thanks for the info. This year the warblers have found them & are having a feast! I will not be doing any type of control, as I prefer having the birds!

    1. We are happy for you and for your warblers. I always say (exaggerating a little) hackberry is a great bird tree, cuz it gets every insect known to man!

  4. I have 2 hackberry trees one is 65 inches in diameter the other 45 inches.. last year they were covered in aphids. I want to out a systemic on them this year but how much do i use and when is best time.

  5. Would the aphids infest the tree if it were healthier? Do they infest older trees that are showing signs of age and rot? What harm does the systemic insecticide do to the berries and birds and butterflies?
    Sugarberry trees grow so large here in Macon, GA and rot from the inside out, split, uproot when very old.
    Great article.

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  7. I have a large Hackberry tree in our back yard that is infested with woolly aphids. Being new to the south, it took a long time for me to find out what kind of tree it is, and what that bug is, and what is this horrible mess they create? I’m done dealing with the mess. Can I treat it myself effectively with a systemic drench, or should I call a specialist to inject the soil? What kind of specialist should I call? Approximately how much should I expect to pay for that treatment? Will the trees berries be poisonous to birds afterwards?

    1. My neighbor has a Hackberry that gets wooly aphids every June. In April, I treat with Systemic drench and it lasts all season. A quart bottle runs $24.99 and one is all you need. The birds and my dog love the berries.

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