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Disappearing Bees & Leaf Beetle

Does anyone really know why so many bees have gone? And, control for insects on Viburnum shrubs.
by Art Drysdale
by Art Drysdale

email: art@artdrysdale.com

Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at http://www.artdrysdale.com


July 27, 2008



Above, first a shot of my Pentas (Pentas lanceolata) at my office door, followed by on of part of the firethorn (Pyracantha coccinea) hedge, both of which are attracting large numbers of honey bees [Author photos], and a microscopic view of the native American Sweat bee (Agapostemon texanus), photo courtesy James Robinson and the York (PA) Daily Record/Sunday News. Below, the egg clusters in a straight line along the underside of young twigs on Viburnum opulus, and a typical leaf with the tiny crawlers (caterpillars) on the underside.
Photos courtesy T. Murray and Washington State University.

A question this week from Jacqui MacGillivray of Tsawwassen, B.C. may well be one about which many gardeners and nature-lovers may have wondered: “I am not sure if this subject has come up before but, is anyone else worried about the lack of bees? I have a big Cotinus coggygria, several large lavenders, many huge (and smaller) containers of flowers on my deck, to say nothing of other bloomers, yet I have seen no more than two bees this summer. Normally, the Cotinus is humming from morning until night, as is the lavender. Does this not bode ill for my, and other, gardens throughout the area (I live in Tsawwassen); indeed, as bees are the main pollinators, does it not bode ill for all gardeners, farmers, etc.? I know we have had two fairly hard winters but I have heard that there is a bee virus in the US; could it have hit here? And is there anything else I can do to attract more bees?”

The “bee virus’ referred to by Jacqui is now known as Bee Colony Collapse Disorder (CCD), and it has spread to roughly half the states in the U.S., as well as to areas in this country. It is also reported in many other parts of the world.

Naturally, it has been attributed to almost every ‘villain’ possible, including, pesticides (insecticides in particular), cell phones, and global warming.

A recent (US) book on the subject, by Rowan Jacobsen, Fruitless Fall: The Collapse of the Honeybee and the Coming Agricultural Crisis, outlines the many problems that have befallen the bee-keeping industry over the decades, but states that Colony Collapse Disorder is the worst, it having decimated the North American bee-keeping industry. Yet, no one seems really to understand the problem, even though it was first noted back in 2006.

Depending on whose scientific studies you believe, the possibility of the culprit being cell phones is no longer a possibility, or it still is. German research, going back a long time has shown that bee behaviour changes near power lines. A limited study at Landau University found that bees refuse to return to their hives when mobile phones are placed nearby. Dr. Jochen Kuhn, who carried it out, said this could provide a "hint" to a possible cause. One of the few known facts about CCD is that bees get lost and do not return to their hives.

One of the interesting aspects of the current research going on in many, many centres is that being done by David Biddinger at Pennsylvania State University’s Fruit Research and Extension Centre, is that it may be possible to replace the honey bees (Apis mellifera). Honey bees are not a native North American species, by the way, but rather imported from Europe to help with pollination back as far as the 1600s, and again in larger numbers in the late 1800s. David Biddinger believes a native bee such as the Sweat bee (Agapostemon texanus) may be able to be coaxed to do what the honey bee has been doing for all these years.

He is soliciting funds to research the Sweat bee as well as others and how they might be used to assist in pollination, particularly for some US agricultural crops that are very much dependent of bees for pollination. One such crop is the almond, which is virtually depends 100 percent on bees, and not on insects at all.

Meanwhile, the losses are incredible. Losses of active hives ranged from 30 to 90 percent in some areas. Many affected bee-keepers indicated that their colonies were under some form of stress at least two months before the first incidence of CCD. Stresses could include poor nutrition of the affected bees (due to apiary overcrowding, pollination of crops with low nutritional value, or pollen or nectar dearth), limited or contaminated water supplies, exposure to pesticides, or high levels of mites. Case studies of beekeeping operations suggested the possible involvement of a pathogen or toxin in CCD. Some beekeepers losing colonies to CCD placed the abandoned “dead out” hive boxes on top of boxes containing strong colonies. These strong colonies also then suffered CCD.

Meanwhile, I must comment on Jacqui’s original note to Donna Dawson, as quoted at the beginning. Contrary to her observations, I cannot say that we have the same situation here in our garden on Vancouver Island. For example, I have a nice standard form Pentas (Pentas lanceolata) in a pot right at my office door, and I seem never to come in or go out that there are not a large number of bees gathering one of their favourite nectars. Likewise, when my firethorn (Pyracantha coccinea) were out in full bloom, there was a continual buzzing all around that part of the garden.

Just room for one more question this week; this one from Cora Lee from near Port Elgin, Ontario: “One day I noticed that my snowball tree in full bloom had the leaves all full of holes - looked like lace. Next day the leaves were all gone and the blooms were turning brown, two days later there wasn't a bloom or leaf to be seen. The tree was here when we bought the house ten years ago, we are located on Lake Huron close to Port Elgin. Our soil is very gravelly. The tree is located on the south side of the house in partial shade. I note there is the very odd green leaf returning to the top branches. Any suggestions would be appreciated. What happened?”

Cora, what you have is Viburnum leaf beetle (Pyrrhalta viburni) which performs a ‘double whammy’ on Viburnum opulus (European highbush cranberry) as well as other closely related species. Unfortunately, the easiest control is to spray to kill the larvae in late May or early June. By now the adults will have emerged, and while they can be killed with insecticide, the are not easily caught with sprays. Early next spring, examine the youngest twigs for signs of eggs in straight lines usually on the underside of the young twigs (see photo). Prune off all of these and burn them or place them in garbage. Once the shrub begins to leaf out, examine the under-surface of the leaves for the tiny larvae. Spray any insecticide to kill them, or pull off the leaves on which you see them.

As I mentioned, the insect does a ‘double whammy’ in that first the larvae eat the leaves (making them into ‘lace’) and then when the adults emerge, they begin eating the new secondary foliage that is put out. Several years of this will kill most subject plants.

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