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lavenderpeony

Aphid infestation on Red Twig Dogwood

LavenderPeony
9 years ago

I have a well-established Red Twig Dogwood shrub. It is close to ten years old. It has always grown very nicely and robustly. Last year, I noticed that late in the summer, a massive infestation of aphids overtook the shrub. The vast majority were black flying aphids.

For a few days, I hosed off the aphids then sprayed the shrub with a homemade dish soap/oil mix. I couldn't keep up - the infestation was so bad that I couldn't get it under control. Come fall, I pruned the shrub very harshly and removed all leaf litter underneath in an attempt to ensure that any overwintering aphids and eggs were removed. As an extra precaution, I sprayed down the remaining branches and surrounding soil with the homemade aphid spray - I did this in the fall then again this spring before the leaves came in.

The shrub sprung back beautifully all spring and summer. Very few aphids and many beneficials all around. Then, come late August/early September, the invasion came again with a vengeance. Same black flying aphids in colonies so enormous I cannot keep up.

Will this continue to happen every year? Is there something I can do to prevent this from happening again?

If this is going to reoccur yearly, I would very sadly prefer to cut down and dig out my beloved shrub.

Comments (17)

  • rhizo_1 (North AL) zone 7
    9 years ago

    Home made concoctions are not likely to be as effective as the commercial products.

    I would try insecticidal soap, mixed according to the label instructions. After leaf fall, I suggest a couple of applications of a horticultural oil, again following the instructions for mixing. Use the oil up until leaf break.

    The aphids may be coming from elsewhere. Winged aphids are born in order to be able to fly from an overly crowded host plant to another....or to facilitating mating, which they only do in the fall when males are born.

    Lots of males are live born in the fall so that old fashioned mating can produce the eggs required for overwintering. The oil applications can not only smother adults, but the eggs hidden in the nooks and crannies on stems.

  • lavenderpeony8
    8 years ago
    last modified: 8 years ago

    Thought I'd post an update. It's been a little over a year since I first posted this. I made it through the whole summer and most of September with beautiful growth and no aphids. Then this week.... and the aphid swarms have returned!!!

    I have a very bee and beneficial insect friendly garden. My backyard is full of good bugs. So, spraying is not an option that I want to try... I know there would be a lot of collateral damage.

    It breaks my heart but I am done with the annual aphid swarm. I just need to be rid of this shrub now so it will have to be chopped down. :(

  • Mike McGarvey
    8 years ago

    Have you been been fertilizing your Red Twigged dogwood? Aphis are attracted to young, abnormally lush new growth, maybe especially so at this time of year.

    Mike

  • wisconsitom
    8 years ago

    At this time of year-with leaf drop right around the corner-it is of questionable value to even be attempting to "save" this foliage. It's done its job for the year. BTW, I happen to live in the heart of red-osier dogwood land and have never seen aphids attack this plant. I'd be interested in hearing your answer to Mike's question. Too much nutrition can cause some goofy things to happen with otherwise fool-proof plants. The very tender young growth of a over-fertilized plant is quite tasty to insects, which is, of course, what he just said.

    Just now noticed you're in Zone 8. I should think it unnecessary to have this particular plant in that rather southern zone, there being so many other options. This is a northern species.

    +oM

  • Mike McGarvey
    8 years ago

    It grows just fine in my northern Zone 8 with no major insect problems, but the Zone goes all the way south into Texas, an almost completely different climate and issues.

    'Chopping' it down won't kill it. It will sprout from the stump with vigor. Dig it out or yank it out.

    Mike


  • gardengal48 (PNW Z8/9)
    8 years ago

    Yes, it is very misleading to associate climate zones necessarily with latitude :-) Cornus sericea is native to just about everywhere in the continental US except for the very most southern or Gulf coast states. It grows wild in my (and Mike's) area as well. And Cornus alba, while not native to the US, is a very widely planted ornamental offering many attractive variegated forms.

    I would really like to see this insect infestation - do you have photos? Leaf blotches or blights are the most common issues with shrub dogwoods. Like Mike, I have never seen ANY insect problems with either the native species or the imported ornamentals in my area.

  • wisconsitom
    8 years ago
    last modified: 8 years ago

    Nor have I. This is easily one of the most carefree shrubs ever.

    +oM

    edited to add: I just looked at the one I've got in my back yard yesterday after work. This was a volunteer shrub that has grown and sent out stolons, such that I could easily divide it into three plants now. In any case, here it is, the very tail-end of September, and every leaf on the plant is a fresh, bright green, not a blemish to be found. I sometimes wonder about folks having trouble with such easy plants as this. Has too much been done? Or alternatively, not enough attention to the one thing Cornus s. does need-adequate soil moisture? That's really about it. Maybe as a final thought, throw in a sweeter soil, not one which is highly acidic. I do notice they resent that.


  • gardengal48 (PNW Z8/9)
    8 years ago

    These shrubs are far more drought tolerant than most would suspect. They are often recommended for dry shade situations and are perfectly content growing naturally in our recurring summer drought climate, which can be extremely dry from early summer well into fall. They are also a suggested planting for rain gardens, which in my area offers the tricky situation of very wet, sometimes flooded winter conditions and very dry, no irrigation/no rainfall summers.

  • rober49
    8 years ago

    I've had good luck getting rid of aphids with large releases of ladybugs. I buy praying mantis egg cases, ladybugs, assassin bugs, & lacewings every year.

  • rhizo_1 (North AL) zone 7
    8 years ago

    How many ladybugs do the mantids nab and the assassin bugs stab, lol?


  • Pink Poppy
    9 months ago

    Oh dear, so sorry it's taken me SEVEN YEARS to reply to your comments! I'm back with another update.


    My beloved dogwood is still with me - as Mike noted, chopping it down did not get rid of it. Though, it did take a couple of years before new shoots started emerging. By that point, I was so impressed with its resilience that I let it do its thing. I've let it grow on and off every other year or so since then.


    Last summer, the shrub grew to a glorious large size and the aphid swarm was correspondingly large (black, winged aphids). It was the worst I've ever seen it - they were attacking even the mature leaves. I had to prune the shrub down to the ground as it was becoming a sticky, aphid-covered mess.


    To answer some of your questions:

    - I do not fertilize nor water this shrub at all, yet it grows lush and healthy all on its own

    - I live in the northern part of Zone 8 (British Columbia, Canada)

    - Dogwoods are native to this part of the world so it's well suited and thrives here

    - I've tried a ladybug release in the past, but they didn't stay on the shrub - they were pretty much all gone by the end of the day!

    - I haven't tried the other beneficial insects yet - willing to consider them but only have a small budget - money's very tight right now

    - Sorry, I didn't snap any photos of the infestations... but I will try to remember to next time it happens


    I'm quite sure I'm giving this dogwood the care it should get... so I'm absolutely confounded by the aphid infestations!!


    Any other suggestions?

  • bengz6westmd
    9 months ago
    last modified: 9 months ago

    I had to give up on a red-twigged dogwood because of repeated infestations of white, rather woolly sawfly larvae of some sort that could defoliate the whole shrub in several days. Happened 3 years in a row and I just cut it down.

  • gardengal48 (PNW Z8/9)
    9 months ago

    With IPM, the first line defense for treating aphids is to spray the plant down with a strong stream of water. This both dislodges most of the aphids as well as kills them. They are soft bodied insects that cannot withstand the force of the spray.

  • Pink Poppy
    9 months ago

    @bengz6westmd Thanks for sharing, and letting me know I'm not the only one who's had repeated pest infestations. Wow, those sawfly larvae are so destructive in such a short time.


    @gardengal48 (PNW Z8/9) I've done this, too, but they come back in full force within a matter of days. I couldn't keep up with it, especially in the years when I let the shrub grow large.


    What about my shrub makes it so irresistible to the aphids?

  • bengz6westmd
    9 months ago
    last modified: 9 months ago

    Pink, here was my red-twig dogwood before getting infested. It was started as a twig thrust in the ground and watered to get it going. It WAS doing fine....



    Pagoda dogwoods also attract sawfly larvae of a different type, and I have to watch out for those, but they are a bit easier to deal with.

  • bengz6westmd
    9 months ago

    There are some kinds of "natural" pesticides like neem oil that perhaps can ward them off. I've used that before on some kind of odd aphid (waxy?) that was infesting a river birch.


    I got my red-twig stem from those growing in many spots along my border stream. I've done the twig-stuck-in-the-ground thing for years along the stream to help control erosion, and it works as long as the newly-stuck twigs are kept moist long enough. Strangely, those red-twigs never showed any infestation. Perhaps because the one above was out in the open on my lawn and thus attracted attention? That's my guess....