A large bed of viburnum davidii in front of our new home is infested with small brown beetles. We are almost sure they are the viburnum leaf beetle, but are not 100% sure. We sprayed the bushes in June with Trounce, as soon as we discovered the problem, but the beetles came back. The bushes cover a large area in front of our house and we estimate they were planted 12 years ago, when the house was built and the garden was landscaped. What would be the best course of action at this point? We are thinking of pruning close to the ground next Spring. Another question is how long it will take for them to grow back. Thanks in advance for any advice.
m--tho davidii is supposedly quite resistant to the beetles, I've also had damage on tinus which is supposedly quite unattractive to them...the little buggers obviously haven't been reading the lists... Your trounce spraying is probably a good choice, but spraying in June may have missed many of the larvae which at that time could have already pupated. The adult beetles evident now are apparently harder to kill, but still could be if you can get the spray in contact with them (they may tend to fall off the plants as you work among them, spray the soil surface underneath the leaves as well!). If the problem persists for several years, the plants could be badly set back, and even die. Plantings back east, where the infestations started years earlier, have been replaced with other, pest free, shrub selections. Eventually, this might have to be the solution here. Apparently, opulus is particularly yummy to these guys, and there are lots of those planted thanks to a UBC introduced variety...yikes. Glen
I find Tinus to be quite prevalent as a host for the beetle (larvae), that and snowball viburnum. I havent seen it much on davidii though.
Many thanks Glen, for your suggestions. We will "trounce" them again early in the Spring, and see what happens. We suspect we might be fighting a losing battle here, as our neighbour's bushes are also infected, and they have little interest in their garden. Any suggestions on a good replacement for the davidii? We also have a hedge along the fence which is infested, but we don't know the bushes, and are still trying to identify them. The hedge is in bad shape. The previous owners cut it back severely, but did nothing to eliminate the beetles. The garden has been badly neglected and we now have to address all these problems we inherited... Thanks again, Mercedes
Mercedes--the eggs apparently hatch out in May, so don't bother spraying too early in spring. And since they start pupating in June, there is probably an optimum time right around May, depending on how warm a spring we get. Broadleaved evergreens like V. davidii? I like choisya, and escallonia if it can grow quite tall. Many azaleas and rhodos are possiblilities too. Paul, the list I looked at from Cornell apparently got some input from the folks at VanDusen, who said that tinus was almost resistant to the beetles. I suspect that info came early on in the history of infesting this area, and the beetles have now moved onto many more species than before. Info on tinus wouldn't be available from back east due to its zone rating, sounds like the list needs updating. Infestation on davidii is even more important than opulus and tinus around here, with all the acres of it that have been installed on commercial landscapes. Sure hope a biological control is found...do you listees in the UK have this pest? Glen
Glen, thanks a million. We will attack them in May. We have a couple of Choisya Sundance in our back yard, they are lovely. I checked escallonia, it is very pretty too. We will keep them in mind in case we lose this battle. If the spraying fails, should we consider cutting the davidii back, close to the ground, as a last resort? My husband wants to cut them back, because he is against pesticides, even though Trounce is not that bad. I dread the idea, as it will leave a huge empty space in front of the house, which will probably take a few years to fill in again. Thanks again, Mercedes
Mercedes, Try this link: http://www.umaine.edu/ceskl/MGNewsletterJune04.pdf it has a couple of ideas on control of the beetle. Thought it might be good timing in case you are getting ready to spray Trounce (please don't!) in the Spring. I'm in your husbands camp when it comes to anything that has "cide" in it ;-) MXB
I think I read somewhere about the eggs being deposited on the newer growth in the summer / fall of the previous year and that pruning in the earlier part of the year may remove a good number of potential beetles. As an aside, I still find Tinus to be the worst affected around here. almost negligible damage to Davidii.
Thank you so much for the reminder and for the link. My husband would not "trounce" them. In fact, he has just pruned them to the close to the ground. However, we have a large bed of ViburnumTinus which is also severely infected. They have been pruned in the past by the previous owners of the house, but have not recovered. We are thinking of removing them entirely. The problem is what are we going to replace them with. Thanks again for sharing your knowledge. Mercedes
We also have it here in the UK, very heavy infestations on V. opulus, Aureum being very attractive to the little blighters, also tinus, i havnt seen it on davidii, by the looks of it, will only be a matter of time.....i shall keep a close eye on the other Viburnus.
We have it here on the Sunshine Coast ....first became aware of them last July/2009...we have quite a number of opulus,davidii,tinus and plicatum...so far the opulus is the main problem but I am now seeing signs of larvae damage on the tinus also found same on a pyracantha that is next to an opulus...we have so many on a large area that we are cutting them down and replacing them ....same problem of the neighbours not trying to control so we are moving on....