viburnum beetle infestation

mutts_fan(z5 toronto)June 4, 2005

My 3 year old arrowwood viburnum has been virtually skeletonized by the larvae of this bug. There is a noticeable bad odour somewhat like dog poop around it, so I first thought it was some sort of stinkbug but after googling around, I found out what it was. Apparently its prevalent around Ontario. I had a highbush cranberry at my previous garden and it had this problem too. Wish I had researched it before I planted the arrowwood.

Thought I should let everyone know in case anyone was thinking of planting one of these shrubs.... beware!

Not only does it look bad, it makes the garden within a 10 ft radius smell terrible!!!

I tried insecticidal soap but the infestation is really too widespread, every leaf has a larva or 2 on it, it seems :( Now we have to spray with carbaryl.

Here is a link that might be useful: viburnum beetle

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knottyceltic(S/W Ontario 5b)

Eww..I think I have this too... my arrowwoods, nannyberries and cranberries are all eaten! What action to I take to prevent even worse from happening?

Barb
southern Ontario, CANADA

    Bookmark   August 26, 2006 at 12:02PM
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treemedic(z4b Ontario)

If you want to go the organic route you need to spray with Trounce or Insecticidal soap (Trounce works better) in the spring when the leaves are 1/4 open and again 7-10 days later. You can also cut then back severly in the winter and get rid of the prunings because the eggs are laid near the tips of the branches. A combination of these two things gets rid of the problem fairly easily..at least for a couple of years.

    Bookmark   August 27, 2006 at 9:14AM
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bonniepunch(USDAz4 AgCanz5a)

This time of year you should be able to see the eggs (or rather where the eggs have been laid). The female hollows out small holes on the newer branch tips and lays her eggs in there, then covers them up with a mixture made up from chewed wood, excrement and other unappealing crud. These branches have a distinctive bumpy or scarred appearance. Cut them all off and dispose of the branches in a sealed bag or burn them (DO NOT compost!!!). Generally it is the newer branches that are affected, but they can go for the older ones too, so look carefully. The adults will be laying eggs for awhile yet, so once the bush has lost its leaves in the fall, give it a thorough going over.

Some people have claimed that they have used dormant oil or horticultural oil with success. This needs to be applied in the spring before the bush leafs out though - applying it after will damage the leaves.

In the spring you'll know you have them when the leaves start developing holes - these are caused by the larvae that overwintered as eggs. If you don't have a lot of them, you could handpick the larvae as you find them (keep a cup filled with soapy water handy and drop them in as you pick them off). You could try spraying with neem oil if you have a lot of them. This has several methods of control and may work (or it may not, it's kind of new and hasn't been widely tested on all insects).

In the late summer and fall is when the adults start in on their damage. They're harder to deal with, since they can fly away. You can try shaking them into the soapy water cup or spraying with insecticidal soap or neem again.

Plants that have been heavily attacked for two or three years will die, so it is important to do something to get them under control if you really want to grow Viburnums!

BP

    Bookmark   August 27, 2006 at 1:23PM
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knottyceltic(S/W Ontario 5b)

BP..thanks for all the info. I have still not actually laid eyes on any of the culprits which is very frustrating.

This question may not be very popular since it's non-organic but isn't there something that I can spray on the leaves that will kill the larvae AND the adults that eat the leaf?

I don't know much of anything about pesticides, so I don't know if other critters would be affected by such a spray.

Thanks for any other info you can offer.

Barb

    Bookmark   August 27, 2006 at 5:58PM
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bonniepunch(USDAz4 AgCanz5a)

It's hard to get a positive ID without seeing a bug :-). Place a white sheet (or a disposable tablecloth, or whatever you have) under the bush. Bang a bunch of leaves, and see what falls out. If it is a beetle about 1/4 inch long and kind of coppery coloured, then it's probably a Viburnum Beetle.

My recommendation is that you stay away from most pesticides. They are being banned in more and more areas for good reasons. Commonly used ones like Pyrethrins, Imidacloprid and Disulfoton will almost certainly kill whatever is eating your bushes. They will also almost certainly kill honeybees and have varying degrees of toxicity to mamals, fish, birds and amphibians. They kill bugs because they are toxic chemical compounds, not because they're highly targeted to one particular bug (like Bt) or because they discourage feeding and growth (like neem oil). You will see fewer butterflies around, ladybugs, lacewings, and predatory wasps will all find somewhere else to call home, and you will have an escalating bug problem with your other plants. Once you step on the pesticide treadmill, it's hard to get off.

I do believe these pesticides have their uses, and when *properly* aplied the danger is lessened. But they are never 'safe'. If you chose to use something like the above, please read the label, do a bit of research, and follow the instructions exactly.

If you can positivly ID your bug as a Viburnum beetle, then removing the twig tips with the eggs and a spring drench with dormant oil should take care of the majority of them. Pick off any leftovers if you see any damage starting. You will probably have to do this every year, since like many imported pests, they are becoming very widespread and they don't have many natural predators.

BP

    Bookmark   August 28, 2006 at 1:49AM
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jancarkner(Ottawa CAN)

WOW, I'm glad I popped in here.. haven't been for awhile. I planted numerous vibernums in my backyard last year (this is our 2nd summer) and mine are being chewed quite a bit. I tried Rotonone earlier, and it seemed to help, but I mostly leave my garden alone, since it's a wildlife garden, and now most are skeletonized. I'll try burning the tips and using dormant oil next spring. Thanks!

    Bookmark   August 30, 2006 at 12:04PM
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knottyceltic(S/W Ontario 5b)

Good gracious...well it's no longer speculation, I DO have Viburnum beetles! The nasty things showed themselves on the day I was leaving for a week vacation but now that I'm home again I am going to take a harder look. I took a quick look while we were unpacking the car and sure enough not only are the beetles there but there are the telltale egg holes all neatly lined up in a row on the tips of the branches. *sigh* I will prune out what I can and treat the leaves with trouce to see if it will "do in" the adult beetles that are still chomping. Boy this makes me annoyed. We have so many viburnum species that half our woods are at risk now. :o/ I'll treat again in spring when the larvae emerge and then again when the adults emerge from the soil. What a bummer :o/

Barb

    Bookmark   September 1, 2006 at 9:57PM
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bonniepunch(USDAz4 AgCanz5a)

Crap :-( it sounds like you have a real job on your hands! Now that you know what to look, for you might be able to keep on top of it though. The Montreal Botanical Gardens had a pretty bad infestation either last year or the year before (darned if I can remember!), and I see very few signs of them this year - so there is hope!

BP

    Bookmark   September 2, 2006 at 3:01PM
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knottyceltic(S/W Ontario 5b)

Well hopefully it won't be too bad of a job. When I say "my woods", I mean "my part of the woods" b/c I just have a city lot sized yard and "my woods" is only one tiny part of a larger woodlot. Still, I've planted a lot of viburnum species so I'll have to keep checking them all now that I've seen the actual bug and know what to look for.

I think I'll "Trounce", then prune, then use the dormant oil in the spring and proceed from there. I'm scared of the chemicals. I once bought a bottle of Malathion (sp?) but have never even cracked the cap because I'm scared of it.

Thanks for all your help.

Barb

    Bookmark   September 3, 2006 at 11:19AM
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