Viburnum lovers must remain on guard for leaf beetle threat

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Marjorie and I love the native viburnums. In her garden’s shady nooks, we planted maple-leaf viburnum (Viburnum acerifolium) and hobblebush (V. alnifolium), two species that prefer growing beneath overhanging branches. They brighten the shadowy realm with their spring flowers, nourish wildlife with their late summer berries, celebrate autumn with the rich colors of senescent leaves. Marjorie counts maple-leaf viburnum as her favorite native viburnum for the unique pink-purple autumn color of its three-lobed leaves.

In sunny spots, we grow arrowwood (V. dentatum), a robust shrub with creamy white spring flowers and cobalt-blue summer berries. And in a wilder section of the landscape where the pileated woodpecker hunts for grubs beneath the bark of spruce snags, we nurture a young wild raisin (V. nudum var. cassinoides) planted by the birds. Wild raisin’s berries change color during the summer from green to pink, then to light blue, finally becoming wrinkled blue-black raisins. In August it is great fun to watch a wood thrush gorging itself, plucking just-ripe berries one at a time from pink and blue clusters, swallowing each berry whole.

When we planted these viburnums, we knew about the viburnum leaf beetle, a pest imported into Canada on a shipment of nursery plants from Europe in the early 1900s. We knew that in recent years it had migrated into Maine, and that it would be a particular threat to native viburnums because their relatively thin leaves made them a preferred host for the pest.

More recently, now that the beetle has become firmly entrenched in Maine, I have seen numerous examples of its capacity to reduce mature leafy viburnums to skeletons of naked twigs on dead or dying plants. “Skeletonizing” is also used to describe the beetle’s habit of eating only the succulent leaf tissue, leaving behind the skeletal framework of leaf veins. Both the larval and adult beetle feed on the leaves, the larvae in spring and the adults in summer and fall, leaving little time between the two stages for an infested plant to recover. It is an insidious death.

But we are hopeful people, Marjorie and I, and we continue to nurture our native viburnums. We carefully inspect each plant in November and again in early April, pruning away and burning stem tips bearing the conspicuous line of crusty egg casings. This keeps the spring larval assault to a minimum. Each year we hope this will not be the summer that hordes of adults descend on the garden from surrounding natural areas, that we will be able to hand-pick most of the tiny brown beetles, permanently interrupting their season-long orgy of eating and mating. This is all that we can do. We agree that pesticides are out of the question. Eventually we may have to give up the joys of gardening with native viburnums, but we will not put at risk the birds and other small creatures which, along with us, dwell in Marjorie’s garden.

For more information about the viburnum leaf beetle, including photographs, visit: www.entomology.cornell.edu/Extension/Woodys/VLBfactsheet2000.pdf. For a map of beetle-infested areas of Maine, go to: www.ceris.purdue.edu/napis/pests/vlb/imap/mevlb.html. Send queries to Gardening Questions, 116 N. Main St., Orono 04473 or e-mail manley@adelphia.net. Include name, address and telephone number.

A selection of native shrubs appropriate for seasonally flooded sites

Editor’s Note: In the April 23-24 Living section, a sidebar should have appeared with Reeser Manley’s column about native shrubs for seasonally flooded sites. The shrubs were selected for their ability to attract and nourish wildlife in the garden. They will thrive in seasonally flooded landscapes while also dealing successfully with summer drought once established. Except where noted, plant these shrubs in full sun.

Buttonbush (Cephalanthus occidentalis)

. Forms dense thickets of 12-foot-high shrubs.

. Fragrant, creamy-white summer flowers borne in dense ball-like clusters.

. Attracts numerous pollinators including most butterflies.

Red osier dogwood (Cornus sericea)

. A colonizing shrub with bright red winter stems.

. Several cultivars available, including yellow-stemmed forms.

. Preferred nesting site for American goldfinch.

Winterberry (Ilex verticillata)

. Female plants produce bright red winter berries crowded on dark gray stems.

. One male plant will produce enough pollen for nine female plants.

. Numerous cultivars ranging in height from 3 to 8 feet.

. Berries eaten by 49 species of birds.

Northern bayberry (Myrica pennsylvanica)

. Spicy-scented leaves and berries on plants growing to 12 feet in height.

. Only female plants produce the berries, so plant a male nearby.

. Waxy berries eaten in winter by chickadees, red-bellied woodpeckers, tree swallows, catbirds, bluebirds, yellow-rumped warblers and others.

. Large thickets offer excellent protection for nesting songbirds.

American elder (Sambucus canadensis)

. Vigorous suckering shrubs growing to 12 feet in height.

. Large clusters of white flowers in spring.

. Purple to black edible fruits in late summer and early fall.

. Tolerant of sun and shade.

. Host to the robin moth, North America’s largest moth.

. Fruits eaten by more than 40 bird species, including all thrushes, yellow-breasted chats and rose-breasted grosbeaks.

. Fox, red squirrels, woodchucks and white-footed mice also eat the fruits.

Meadowsweet (Spiraea alba var. latifolia)

. A small shrub growing to 4 feet in height.

. White to pale pink, summer-long flowers in multibranched clusters.

. Nectar source for many insects, including bumblebees.

. Host for spring azure butterfly.

Steeplebush (Spiraea tomentosa)

. A small shrub growing to 4 feet in height.

. Summer-long spires of rose-pink flowers.

. Nectar source for many insects, including bumblebees.

. Host for spring azure butterfly.

REESER C. MANLEY PHOTO

JUMP PHOTO CAPTION:

REESER C. MANLEY PHOTO

In autumn, maple-leaf viburnum is distinguished by its pink-purple foliage.