This message received via email: We have an old tree we call the snowball tree (big round white flowery balls at this time of the year). Anyway, it has got tons of small worms/bugs that are completley eating the leaves and leaving them lacy. The worms seems to start at the bottom of the tree and eat their way to the top of the tree. We were wondering if we can buy some sort of chemical(?) or something that we can put on the base of the treee or the leaves to stop and kill the worms. I hope my description is fairly understandable.
Snowball tree is a common name for a couple of different viburnums. Yours is probably Viburnum opulus 'Sterile', an old cultivar that reaches tree-like proportions and one that many would consider somewhat bulletproof. Yours is not the first posting in the forums to discuss "little green worms." In fact, this year seems to be a very good one for caterpillars in the Vancouver area. Perhaps this is a "peak" year for this pest. Although the damage looks frighteningly severe, it is probably not going to do the plant any lasting damage (most of the eaten leaf is returned to the soil out the back end of the caterpillar) and the attack will probably be short-lived. People sometimes apply Btk (Bacillus thuringiensis var. kurstaki -- a naturally-ocurring bacterial disease of caterpillars) to the leaves of similarly affected plants. Once caterpillars ingest tainted foliage, they soon stop feeding and die. Btk is generally acceptable to organic gardening advocates, since it breaks down quickly in sunlight, is specific to caterpillars and has little or no effect on other organisms. UBC Botanical Garden does not generally recommend the use of synthetic pesticides. There are many reasons for this, but foremost among them is that the use of pesticides typically upsets ecological balances that naturally develop in landscapes (e.g., natural predation, parasitism, and antagonism by other organisms). The caterpillars will do some damage this year, but In all probability, damage will be less significant in subsequent years. In many cases, the application of pesticides will more severley affect predators, knocking them back harder and allowing the target pest to rebound more quickly. In other cases, pesticides have been known to eliminate a major pest, only to replace it with a secondary pest, which now, freed from competition with the original pest, becomes a serious pest itself. The development of resistance by pests to applied pesticides is also a serious issue. Finally, health risks to humans and other organisms with many commonly used pesticides are significant. A number of local municipalities have decided, for example, that the cosmetic use of pesticides is completely unjustifiable (and certainly a significant liability issue). An alternative approach to pest control is to create more diverse landscapes. Where there are habitats and microhabitats for a variety of organisms, the effects of pests on any one plant are generally reduced. Severe outbreaks are uncommon in such landscapes and there are lots of interesting organisms to look at. For example, a small pond with adjacent upright "branchy" vegetation is attractive to dragonflies, which are effective mosquito predators. Shady and sunny areas, open water, ground cover plants, mulched areas, trees, shrubs and herbaceous plants all attract different kinds of organisms. Each acts to feed, cooperate, antagonize, compete or prey upon something else. One has to put up with a certain amount of ocassional untidiness, but the end result is undoubtedly better for the neighbourhood.
I hate to disagree with Doug but, I think the problem you have is Viburnum leaf beetle which unfortunately BTk will not control, reccommended control is a broad spectrum insecticide such as Diazinon, Methoxychlor or Malathion. A 3 year return of infestation can be enough to kill the shrub. For more information try this link: http://www.agf.gov.bc.ca/cropprot/newpest.htm#viburnum
I don't have enough experience to diagnose a pest problem based on a description, but if it is indeed viburnum leaf beetle instead of generic caterpillars, there are organic methods of control. The Department of Horticulture at Cornell University has put together an excellent web site on viburnum leaf beetles. Here are some links: Viburnum leaf beetle home page (with links to more specific pages) Managing viburnum leaf beetles (includes organic methods) How to identify viburnum leaf beetles
Ihave just found this pest on two of the trees I have ,it is small worm like ,the leaves on the entire trees were infected & are now bare,I am told it was a Stink beetle lavae, the leaves looked like a fine lace .Has anyone any idaes to prevent it from reoccuring .
Three years ago our gorgeous Snowball Viburnum also was infected with worms, for the first time. The worms ate through every leaf. It was a mature bush but didn't bloom that year because of the leaf damage. The bush looked awful after the worms finished their chewing. Last year the same thing happened. We decided that if it the worms showed up again this year the bush would go. This year the leaves didn't even mature before the worms started chewing through them. Yesterday we chopped the whole thing down. It was over 12 feet tall and nearly as wide. It broke my heart to do it but we avoid using any kinds of pesticides on a big scale like that, especially since we have many other trees, bushes and other plants growing close-by, including berry-producing bushes. I checked the great links you all provided on this forum and it does look like it was the Viburnum leaf beetle. Very destructive critters. We live on heavily treed acreage, with a large variety of trees and bushes, and every few years we get some kind of caterpillar infestation on a couple of certain mature deciduous trees. The caterpillars leave those trees totally bare of foliage. That usually lasts only one year at a time and it usually takes a couple of years for those trees to leaf out in full again. That's a cycle we've learned to live with for over 40 years, regarding the same trees. Doesn't seem to do the mature trees any lasting damage. But our poor Snowball Viburnum went through the infestation trauma for 3 straight years. We've never seen anything like it. Those Leaf Beetles are relentless.
If it is indeed Viburnum leaf beetle, the only effective control I've seen for a large Viburnum is removel & replacement with a resistant Viburnum. Generally, Viburnums with thick or furry leaves are resistant, with some exceptions. http://www.hort.cornell.edu/vlb/suscept.html It's been a pretty effective pest in the Northeast NA....don't know why the nurseries are still selling European Snowballs?
Thought some of you might be interested in the collage I have of my Snowball tree. Not sure it will survive this infestation. You can see different looking worms, aphids, small mealy type bugs etc. Hopefuly you can zoom in and get a closer look. I pruned back hard as you can see by some of the wood on the ground. Am considering taking a chainsaw to it in hopes that it will regenerate next year or I may try to remove it entirely and start again. Would appreciate any suggestions or comments. Thanks for your time. Later.... Erle from Cambridge, Ontario
The same thing happened to my snowball tree. It literally disappeared within 1 1/2 weeks. Do you know what type of insects these are? Will they harm other trees or bushes? Did you have to cut down your tree or can it possibly recover? Thanks.
Viburnum Leaf Beetle eradicated http://www.durgan.org/URL/?Larvae 9 June 2009 Viburnum Leaf Beetle The two viburnum trees were spayed about five times over three days and all the larvae have been destroyed. I used my home made sprayer which made dispensing the rhubarb and soap in water easy to dispense. Next year I will start spraying at the first sign of infestation. Action taken was a bit late but at least all the vegetation was not destroyed. http://www.durgan.org/URL/?YJTPX 19 March 2009 Spray can for garden use.
Stop cutting down perfectly nice shrubs. Start spraying (particularly the underside of the leaves) your Viburnums with good old soap and water (maybe even a bit of alcohol) on a regular basis and kill the beetles. Further start pruning out deadwood on the plants, dormant oil spray in the spring and fall, and don't fertilize. Snowball bushes are wonderful traditional plants and will be just fine if you put some effort into them. You cannot expect they will perform in a highly urbanized environment without a little help. As mentioned there are lots of varities of viburnums with lovely flowers, more rugged leaves, and less susceptibility to leaf beetles. Check out Michael Dirr's Viburnums. The increased biodiversity in the garden is great but is hard to achieve and often not enough to control a persistent, multi-generational pest. By all means encourage birds and dragonflies but in some circumstances man needs to intervene directly. Read Doug Tallamy's Bringing Nature Home to get a better perspective on how to bring wildlife to your yard and why insects are necessary to this process.
Noticed today that around a dozen new leaf shoots have appeared. Expect the beetles to appear in about three weeks from now. Have repositioned the bird feeder in about the only place where the squirrels can't get at it. (Thats another story) With the birds back in force, my two gallon sprayer filled with soap and water, I expect that the coming battle will be eventful and merciless. I would like to thank all, for there is no doubt in my mind that a true champion will emerge from the ensuing carnage. (Trust it will be me) Later........... Erle
Better than a pump sprayer is a hose end sprayer that mixes concentrate for you. THis way you can soak the entire plant with gallons of water versus squirts from a pump sprayer.
I'm going to try the 40 parts water to 1 part dish soap method touted by Ed Lawrence on CBC radio. This bush has been infected for at least five years and is hanging on by a thread. It seems to bounce back every year but by summers end there is not much good growth left on it. I'm going to try spraying the underside and top with this formula, let it sit for 10 minutes and rinse the whole thing off with water. The pest is a little black worm I think, very small. We are in the GTA area of Ontario. I will follow up with the results in a few weeks to let you know how this worked for us
