aNo one told me when I was falling in love with my viburnum that danger could be lurking at any moment.
I bought the plant several years ago and put it just outside my bedroom window. In the early mornings in spring, when I opened my shades to let in the sunlight, I could see the plant's growth through the bud and flower stages and then later when leaves filled the shrub's woody branches. I could open my window in May and cut white blossoms to fill vases on our bedside tables.
And then something devastating happened. Even if I had been more diligent when I admired it each morning, there's a good chance I wouldn't have seen the pest that attacked this plant I had grown quite fond of over the years.
I brought it home when it was barely 18-inches tall. I put in the exact spot the directions suggested, sunny most of the afternoon but tolerant of a bit of shade from a nearby conifer. I planted it just close enough to the house so I could reach out from the window and touch it, but far enough away that it had plenty of room to spread.
With more than 150 viburnum varieties to choose, I opted for the most common, Viburnum macrocephalum, or snowball viburnum. I knew this plant can get quite large - up to 20 feet high and 15 feet wide - but I wasn't against a bit of pruning to keep it within the boundaries of that particular spot. Every year, I watched the plant get stronger and more mature. It thrived and this year is expected to reach at least six feet tall. It probably will be and started showing signs that it would need a bit of pruning soon.
And then disaster hit.
I went out of town for a few weeks in early May. Before I left, I watched the plant throughout the spring from the time the tender young leaves started poking out from the branches until just before I left, when the flower buds were swelling and getting ready to burst. I anticipated seeing the shrub in full bloom when I returned.
The night I came back, the shades were closed and I didn't bother opening them. But the next morning, when I pulled them open to let sunshine into the room, I was shocked to see the withered, decimated leaves and wilted, brown flowers. On the underside of what was left of a few skeletonized leaves, were small, pale yellow worms.
I called my husband in to look at the mess that was once a lovely, lush plant. He, too, was shocked. He was home while I was away but hadn't noticed the disaster that was taking place right outside the window.
''I think it's dead,'' he said, and it certainly looked that way. But a few days later, he called me at work to tell me there was new growth on the branches. Tender young shoots, just like we saw in early spring, were emerging from the very branches we thought were goners.
After a bit of research, it became obvious my plant was hit by the Viburnum Leaf Beetle. Believed to be from Europe, the pest was only just discovered in Ontario in 1947 and it was seen in the U.S. in 1996 in northern New York state. Although it still hasn't traveled far, once breeding populations were discovered in 1978, it didn't take long for the pest to travel through parts of Maine, New York, Vermont, Massachusetts, Pennsylvania and now Ohio.
Here are a few things I found from Cornell University's Insect Diagnostic Laboratory website:
l The insect's life cycle begins mid-to late-summer when the adult beetle lays its eggs in pinhead sized cavities it has chewed into the undersides of branches, usually - but not always - on the current year's growth. The beetle seals up the hole and the larvae overwinters there only to hatch in early spring to feed on the leaves. By early summer, the larvae crawl down to the ground where they burrow into moist soil and pupate. In July, the adult beetles emerge, feed on the plant's leaves and start the cycle over again.
l Some viburnums are more resistant. Cornell University categorizes these as highly susceptible, susceptible, moderately susceptible and resistant. My species is listed as moderately susceptible, indicating varying degrees of damage and fortunately, not always certain death.
l There is a manual control, which is to find the egg-laying sites between early October and mid-April and prune them out. According to university information, the eggs are easiest to see in winter when the leaves are gone.
l Even though this insect is not native, there are predators. Adult lady beetles and spined soldier bugs eat adult beetles. Encouraging beneficial insects to the garden can help. Using pesticides kills beneficial insects, so if you see these predators, don't think they are attacking the plant too and start pulling out the sprays. Let nature do what nature does.
l This is my favorite. Since the larvae crawl down the shrub's trunk, applying a barrier such as an insect trapping adhesive can stop the larvae from completing the cycle. Check local garden centers for sticky insect trapping products.
l Fortunately, there is only one generation each year of this insect. In addition, this insect only attacks viburnums, which means if you have an infected plant, you don't have to worry if nearby plants will be affected.
For more information on the Viburnum Leaf Beetle, check out the website: www.hort.cornell.edu / vlb/ or call the Trumbull County Master Gardener horticultural hotline at 330-637-3908.