I've been searching online for days and am no further ahead. We recently moved into this house and a couple months ago, I noticed that half of our tree in the front yard was dead. Upon closer inspection, I noticed that the leaves of the remaining half were all chewed and holey and upon even closer inspection, saw little brown caterpillar-things (I hesitate to call them caterpillars as they were only about a half inch long). Assuming they were caterpillars anyway, I called a bunch of gardening places in search of btk but came up empty. Fast forward a few weeks (got sidetracked) and I noticed millions of little black aphids on the majority of the stems. Then I looked underneath the leaves again and saw these white things that looked again like short caterpillars, but they were immobile and sticky. Pupa? Larva? I have no idea - I am COMPLETELY clueless to the whole gardening thing and flying by the seat of my pants here. Any ideas as to what I'm looking at and how to save what's left of my poor tree? Or is it done for? Thanks in advance!
Probably viburnum leaf beetle, searching this site and others will turn up additional discussion of this new (to us in this region) pest. Aphids have long been apt to appear on common snowball (Viburnum opulus 'Roseum'), which your shrub is likely to be. Control of these will involve different approach than that of the beetle. Note also that viburnums renew themselves from the base with new canes orginating there, as do roses, lilacs, raspberries and other "cane growers." The pruning of yours into a lollipop tree, with a limbed up base and congested ball-like top is not optimal for this particular kind of shrub. Maintained in a more natural fountain-like, less dense habit it would also be more impressive in flower, a sort of living bouquet.
looks like two different pests. in the middle picture you can see the blackish colored aphids lined up on the stalk with "caterpillar" like leaf chewing on the foliage. i'm not sure the identification of the white worm in the last picture, but i bet that is what is doing the major damage you are seeing. the aphids won't make those big chomping bites like the worm since they have piercing/sucking mouthparts. they usually make small, yellowish spots on the leaves when they suck out the chlorophyll. i just looked up the viburnum leaf beetle and the larval stages look very different. it is more brownish/black, but the damage they cause is VERY similar looking. i bet someone has the answer. http://www.hort.cornell.edu/vlb/
Yeah, that's right I've seen pictures of those before too. You would expect initially that these are caterpillars, watching or picking one to see if it moves along on multiple sucker-like feet would confirm that. The severe damage, geographic location and host fit the beetle so that's why I thought of that.
I don't know what those white worms are either but if they are eating leaves (and it looks like they are) it maybe doesn't matter too much - they're certainly no rare butterfly if they're in such abundance, and since they seem to be evident during the day they should be easy enough to hand-pick and step on; that'll help the shrub the quickest. You can also simply cut off those really heavily aphid-infested branches and discard them - no need to preserve the branch tips at all costs, and that gets rid of the most aphids the quickest. The pruning will generate some new growth, however, so don't do it too late into the summer or the new growth won't harden off by winter, plus generating a lot of new growth is a burden on what is obviously already a stressed plant. As Ron says, a little new growth won't hurt the looks of that shrub at all!
maybe the white caterpillars aren't the culprit? maybe they didnt' get a picture of the actual viburnum leaf beetle. like you said, with the location, plant host, and damage all signs point to that.
As an addendum to what I wrote above, I do have some concerns about recommending that you kill an insect when you don't know what it is - only if you definitely observe that these beasties are doing the damage you're concerned about should you do this. A few years back I wondered what some odd larvae were that were hooked into my Philadelphus (mock orange) shrub leaves - but I didn't kill them as there was no obvious damage. They turned out to be ladybug larvae, so I was glad I hadn't. (These white things are NOT ladybug larvae, incidentally). Even if you are sure they are the source of the damage, I wouldn't give up on identifying them first. Books are really a far better way to do this than the internet - as you can flip through the book looking for the picture you're after much more easily than you can "flip" through the internet, and on the 'net you just can't do a systematic search - it's always somewhat random. I also wouldn't rule out the child's trick of putting one in a jar with some leaves to see what it turns into, which may work if it stays alive in that environment.
Thanks for all the replies - I checked out the beetle and the larvae photos DO look similar to what was there before (the brown things I mentioned) - I'll admit I didn't get too close but they did look like this in shape and size, only they were a darker brown. I know the aphids are a separate issue and we'll get to pruning this poor tree as soon as possible. Snowball sounds about right - it used to have big tufts of flowers on it. :-( I'm so green (and not in the good way). I'll look some pics up to see the proper shape. Ah, the joy of homeownership! I don't think these white things are what caused the damage - it hasn't gotten worse over the past few weeks. Besides - I pulled off a couple leaves and have been watching the white things and they don't move, nor do they react when I touch them (with a twig, of course - ew). The leaf I took the picture of, I've had that on the deck for two days and the white things haven't budged. They're in some kind of dormant state - pupa, perhaps? Thanks again for the comments. I think we've narrowed it down. I'm guessing the white things are the beetle pupa, but dang if I can find a similar picture online! Time to hit the library!
Update - I finally found a photo. Could these be cottony cushion scales, or are those even around in BC? Although, it does sound like they're not leaf-eaters. Argh. So confusing.
Yes, actually, before I read your remarks the VERY first thing I thought of - upon seeing your picture - was scale insects.
i would think scale too. i think your picture was so good and close up that they apeared larger than they actually are. I was scouring the internet and books yesterday looking for larvae of beetles, butterflies, and moths, even slugs and never found anything that closely resembled the white bugs. they do look a lot like the scale, which would explain why they haven't moved.
most effective method i have found is a dormant oil spray. of course, this is only applied when plants are dormant in the winter. the scale may or may not be worth trying to treat, depends on severity. if severe, they can cause branch dieback. this year i have tried a soil drench application of a systemic insecticide on some red maples that have their bark completely covered in gloomy scale. it is so bad you can barely see the actual maple bark! i would rather not resort to chemicals. but we really didn't have much choice in this situation. not really sure of your regulations on pesticides in BC? maybe someone locally can give better alternatives?
With scales generally it seems the recurring recommendation is that you attack them at the vulnerable crawler stage, when they are tiny and moving around. Timing is critical, you must spray during that stage. Not saying, however that is the only approach that is ever used.
Kind of looks to me that two of your stocks on that plant have died off regardless of insect pests. Insects wouldn't have caused that. Nasty pile of Aphids, and from what can be seen there does look like Viburnham beetle Larvae damage too. No idea what those white things are, although they do not look like any major pest, they just look like something pupating there. Check those dead branches and see if they all lead back to the the same trunks. Some natural causes may have killed off part of your plant. Regards Jim.
