2007-10-27 / Outdoors

Invaders destroying wildlife

Much of our outdoor community overlooks the importance of native shrubs to our forests. There was a time when wildlife relied heavily on them for both food and cover. Overbrowsing by deer resulted in their scarcity in our forests.

However, in recent years with the reduction of our deer herd, native shrubs are becoming more prevalent.

One species that has made a comeback now faces an even more serious threat: a leaf beetle that has a seemingly insatiable appetite for our viburnum species.

These shrubs produce berries that are relished by birds, including grouse. Some of the fruit is tasty and fit for human consumption. Viburnums also produce good browse for deer, rabbits, elk and hares. They sprout beautiful white flower clusters in springtime.

Our native viburnums include arrowwood, American cranberry bush or high bush cranberry, nannyberry, wild raisin or witherod, hobblebush, and maple-leaf viburnum.

Like most exotic pests, the viburnum leaf beetle was introduced into North America from Europe with nursery stock. It was first observed in Ontario and has been spreading southward.

I first noticed it at Sinnemahoning State Park in 2005, defoliating arrowwood plants. Since then I have experienced problems on arrowwood, highbush cranberry, and nannyberry that I have planted for wildlife, and have noticed it on maple-leaf viburnum in the wild.

After hatching in the spring, larva feed upon the newly forming leaves of the viburnum, causing moderate defoliation. The larva then drop off the plant and pupate.

When adult viburnum leaf beetles emerge in July or early August, they are plain brown. They rapidly defoliate viburnums, skeletonizing the leaves so that only the leaf veins remain. The shrubs at this point often appear dead. After several years of defoliation, they do indeed die.

The adults feed heavily up until the first frost. When disturbed, adults have the tendency to drop off the plant onto the ground as a defense.

Prior to the first frost, the adults disperse to new viburnum plants. Females chew out holes in viburnum branches. They then lay their eggs in the holes and cover them. Usually, these egg clusters appear as raised bumps in a row that stand out drastically due to their color.

It is inevitable that our native viburnums will suffer from these invaders and our forests will become less able to support wildlife.

Good luck to turkey hunters who head out for Saturday's opener. Turkey populations will likely be centered in areas with heavy white oak acorn mast.

In areas without white oak trees, wild grape, beech, hawthorn, and cucumber magnolia mast are all favorite fall foods of turkeys.

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