Tiny bugs all our fence!
November 13, 2009
We live in Philadelphia and over the past few months part of our back yard fence has been colonized by these small (3mm) insects. There are hundreds of them. The fence runs underneath a weeping willow tree, and they appear to also be on the willow. The bugs move fairly quickly. I’ve tried sweeping/blowing them away, and they return hours later. When you squish them it leaves a purple residue. Our landscaper thinks that based on the speed of the insect, that they’re probably a “beneficial”. Any thoughts?
Sam Blackman
Philadelphia, PA (Northwest corner of the city)

Unknown Hemipterans

Black Willow Aphid

Hi Sam,
WE are not having much luck with a definitive identification.  At first we thought these were immature True Bugs, but we cannot find any images that match.  Then we thought perhaps they might be Aphids, which are in the same insect order as the True Bugs. There is a
Giant Willow Aphid, but it doesn’t match your specimens.  We think we need to seek assistance from Eric Eaton and our readership on this identification.

Unknown Hemipterans

We were not content with giving up, and we located a reference on the UMN Yard and Garden News website for a Black Willow Aphid, with no scientific name.  It is described by Jeffrey Hahn as:  “Black aphids with orangish or brownish legs and cornicles (the tail pipes of an aphid) on willow are black willow aphids. They are large for an aphid, reaching up to 3/16th inch in length. They can be quite abundant in August and September. These aphids are common on willows and may also be found occasionally on poplars and silver maples.
Black willow aphids secrete honeydew, a sticky sugary substance which will coat any object underneath an infestation. Yellowjackets may be attracted to infested trees because of the honeydew. In addition to being a problem in trees, these aphids sometimes have an annoying habit of dropping to the ground and collecting around buildings and nearby objects. If their bodies are crushed, they can stain siding and other objects a blue-purple color.
Despite their abundance, they do little if any lasting harm to established, vigorously growing trees. Their presence is just a nuisance. Tolerate these aphids as much as possible. If you wish to reduce their numbers, try washing them off as many branches as you can reach with a hard spray of water.  … If nothing is done, their numbers will diminish on their own by the end of the month.
”  That led to an image on Flickr with the scientific name Pterocomma salicis.  That brought us back to BugGuide.  The images online of the Black Willow Aphid are spotted, but other than that, they resemble your insects.  We still hope to get assistance with this ID.

Unknown Hemipterans

Black Willow Aphid

I think it might be a willow aphid of sorts, just not the one you were thinking of.  I think these might be Pterocomma salicis instead, but I am by no means positive.  At this time of year aphids are changing to alternate host plants for the winter, too, so that can really throw things off.  Aphids of the same species can, in at least some cases, look completely different depending on whether they are on the primary host or the alternate host.

25 Responses to Probably Black Willow Aphid

  1. Colleen Smith says:

    We have a lot…. Millions… Of these bugs. It is awful!! They are all over the kids toys, swing set and killing my willow tree. I really need help getting rid of them. I won’t let the kids outside now. I spray them with water and they come back. What should I do???

  2. Carol Braun says:

    I am experiencing the same problem. They are covering my tree, and other objexts siting in my yard, like our garbage cans. I am spraying them with a mixture of Dawn dish soap and water. They are still in our tree, but I spray around the house etc and have noticed they have slowed down. After spraying, the bugs are kinda dried out, and don’t leave a purple stain like when you crush them.

  3. Mohsin says:

    In green house i planted willow seedlings from last week i oberving the coleoptra in willow ports. could you suugest me any kind of solution to get rid off from these tiny insects.

    • bugman says:

      Spraying the infested plant with mild, soapy water is a long established method to control Aphid populations.

  4. paule says:

    These have just shown up. We’ve lived here for 30 years with large willows and never have seen them before. Thousands upon thousands. Insecticide kills them on contact but seem to be impervious to the residue of the poison and does not affect them. Can’t spray the tree cuz it’s over 60ft tall.

  5. Kimberly Weggeland says:

    I have been searching for days and I finally have somewhat of an answer. I am happy that I found this because I have the same issue as stated above and it has really been “bugging” me. Thanks for writing this!

  6. Melissa Engelhard says:

    Are Black Willow Aphid harmful to chickens? They are all over the outside of my chicken coop.

  7. Rachel says:

    Here in Minnesota we had these insects ALL over our backyard. I’ve never seen them before until this year. I did as much research online as I could and came up with nothing till this post. I will say that we did spray with an insecticide. However we ended up spraying the hanging branches of the neighbors weeping willow tree. That worked like a charm and they haven’t come back.

  8. Lisa says:

    Same here! Our Southeast Michigan yard is infested with millions of these, identical to these. They just appeared—first time in 25 years, and there is a huge willow in our backyard, being taken down as we speak. Hoping for a solution, as this is tge stuff of my nightmares!

    • Amy says:

      Since you removed the tree did the aphids go away? I’m considering getting mine taken down as well but only if it will for sure solve the problem. Thanks!

      • Lisa says:

        So, here’s the crazy thing. Yes! The bugs disappeared the day after the tree was taken down. It was as if they were never there—completely gone after the willow came down. We haven’t seen them since!

  9. Pattie Cavalletto says:

    It seems that this is what we’re being plagued by, here, too, in northeastern New Mexico, in 100 year old Black Willows, Salix Nigra, imported historically from somewhere “back east”. I appreciate reading these accounts so much, thank you everyone, it really helps to finally know something. Our trees are huge, so, don’t know how we’ll deal with them, and are praying they don’t come next year. These same trees had a few of the same black aphids, one year in the 1980s, and none again until this summer. This year is a far more serious infestation, and the trees are looking quite stressed, but it’s also nearing fall. Yes, the stuff of nightmares, I agree!!

  10. tdlemon says:

    first time in 30 years to ever see these little bugs. a pain in the azz. I have been spraying the side of the house and other objects in the yard. hoping a first freeze will eliminate them. weeping willow is over 30 years old and we never had an issue till this year. a purple/grape goo if smashed.

  11. Pattie Cavalletto says:

    I’m hoping the first freeze will kill the aphids. I was told by a tree pro that the best war to kill these aphids is by using a systemic with imidacloprid around the base of the trees. This insecticide is a neurotoxin known to kill honeybees. He said it would take 5-6 weeks for it to be fully transported into the leaves and become effective. Not wanting to add to the die off of honeybees, I’m wondering about applying next season after trees flower, hoping to miss doing harm to bees. Perhaps by then, I might know if we have a return of the aphids, not ever wanting to go through another summer like this one, I will try it if nothing else presents itself. I wonder if anyone has any experience with trying this approach. Also, if anyone has a successful idea for cleaning off roofs and stones covered by months of honeydew. Beautiful flag stone paving is blackened, and so far, scrubbing with various house cleaners hasn’t done much good.

  12. Debbie Larrad says:

    Saddened to hear any use of pesticides being discussed- when we already know our bees are dying. I have this same problem on my willow screen, but will instead do anything i can – such as letting the birds and ladybirds help by introducing bird feeders to this area – the birds can’t see the aphids unless they get up close, and ladybirds are there and feeding on them. Also, please note that the bees feed on the sticky honeydew the aphids produce so don’t use presticides please.

    • bugman says:

      Dear Debbie,
      We agree with you, and we were puzzled by your comment since What’s That Bug? does not provide extermination advice, nor do we promote pesticides. Upon rereading our posting, we realized one of our quotes included a comment about insecticidal soap, so we removed that sentence from the quote, replacing it with an ellipsis. Thanks for bringing this to our attention. Comments from our readers do often include extermination advice.

  13. Patricia says:

    We have a corkscrew willow which we believe to be hosting these aphids. They are very few that we can see on the willow itself, but they are all over our wooden deck and metal furniture. We can’t use our deck now!

    First time this problem and the tree is around 15 to 20 years old, maybe more and over 40 feet tall we guess.
    Very discouraging. It we hope the cold coming might slow them down and we will use dormant oil spray in the 2020 spring.

  14. Patricia says:

    We have a corkscrew willow which we believe to be hosting these aphids. They are very few that we can see on the willow itself, but they are all over our wooden deck and metal furniture. We can’t use our deck now!

    First time this problem and the tree is around 15 to 20 years old, maybe more and over 40 feet tall we guess.
    Very discouraging. It we hope the cold coming might slow them down and we will use dormant oil spray in the 2020 spring.

  15. Pattie Cavalletto says:

    The good news is that one year is unlike another. After the summer of 2018 when our black willows were plagued by aphids, they didn’t reappear in 2019, and the trees recovered beautifully. This year has been much rainier than last year, so, I think that had something to do with the invasion we had. I apologise for mentioning an insecticide, I hoped something knew about how to use it skillfully. With such huge trees, I couldn’t imagine ladybugs making a difference before flying away, I really appreciate knowing they amy have worked for someone else.My actual worst nightmare would be to lose my trees, and I’m so glad they’ve survived and done well again.My sympathy goes out to those who felt they had to take down these gorgeous trees.

  16. Engineer, Dave says:

    I am an engineer at Tiny Town, Colorado. At the park we have 7 Willow trees over 60 feet tall. We have a whole bunch of sapling willows along our creek bed. We have had a commercial spray company spray the large willow near the playground, with good results. They stated that they could not spray near the creek bed. That leaves the remaining willows still infected. My question is will these Willow Aphids winter over here in Colorado? This is the first time we have been infected in the last 16 years.

    • Val says:

      I’m in Deer Creek Canyon, CO, and seeing the same on my huge willow. First time in 25 years up here. I’m hoping they die over winter. Friend at UW said to dust with flour, which constipates them. Alternative is Neem or horticultural oil. Haven’t heard of using flour before, but if it annoys the bicyclists as a side-bonus, it’s worth a try. Would need to engineer a dusting method for a tree this tall… Suggestions?

  17. Robin says:

    Can these black willow aphids harm your pets?

Leave a Reply

Your email address will not be published.