Gypsy moths: unwelcome guests with big appetites - using natural controls to prevent annual defoliation

Flower & Garden Magazine, August-Sept, 1994

European gypsy moths have been unwelcome guests in Northeastern and middle Atlantic states since their accidental release in 1869. Cursed by gardeners, environmentalists and foresters, gypsy moth larvae can strip a hardwood forest bare of leaves in a matter of weeks.

The populations of gypsy moths surge and wane from year to year, making newspaper headlines in the years of worst infestation. Healthy trees that are defoliated in spring usually leaf out again by late summer; trees that are stripped clean in two or three successive years, however, may be killed.

Over the years, an arsenal of insecticides has been used in the battle against the gypsy moth, from DDT to Bacillus thuringiensis. Despite the chemical and microbial assault, gypsy moths continue their slow advance across the continent.

Some scientists now believe that the best defense against gypsy moths is to introduce and encourage a broad base of the insect's natural enemies. In the gypsy moth's native region (Europe and Asia), outbreaks of the insect that lead to widespread defoliation are infrequent and quickly controlled by natural predators and diseases.

American scientists are seeking out these natural enemies, including parasitic and predatory insects and pathogenic fungi. Still under study, but showing early promise in tests by the U.S. Forest Service, is a virus that causes a fatal disease to sweep through the gypsy moth population. Such natural enemies don't prevent outbreaks of gypsy moths, but can reduce their severity and perhaps slow the spread of the insects.

The discovery of a few Asian gypsy moths in the Pacific Northwest has brought new urgency to the attempt to control these pests. Unlike the flightless European gypsy moth females, adult Asian gypsy moth females can fly. Should the Asian species gain a foothold in North America, it could spread at a rapid pace.

Banishing Bambi

When deer munch on prized plants, gardeners try all sorts of tricks to keep the animals at bay. Several Earth's Garden readers have written to report success with a simple, inexpensive fencing technique. Constructed of monofilament fishing line strung between stakes spaced 15 feet apart, this fence would not seem substantial enough to keep any animal out.

Jens Thomsen of Fortuna, California, wrote to describe his fence. "I take 20-pound fishing leader and string it horizontally on poles around the garden, approximately 18 inches between strands and to a height of 6-1/2 feet.

"Deer will come up and look at it, but never jump through it, or over it," Thomsen writes. "For the past three years I have had 100 percent success in keeping deer out of my vegetable and rose garden."

Because the fence is nearly invisible, it's a good idea to point out its location to garden visitors, and to mark it with strips of cloth.

Landscaping to Save Energy

A good home landscape creates an attractive frame for the house, as well as pleasant spaces for outdoor recreation and relaxation. Appearance is usually the foremost consideration as homeowners select and place landscape plants.

A thoughtfully designed home landscape can also cut utility costs, as detailed in Energy-Efficient and Environmental Landscaping by Anne Simon Moffat, Marc Schiler and the staff of Green Living (Appropriate Solutions Press, 1993; 230 pp., $17.95). The book is a practical guide to environmentally conscious gardening techniques, with an emphasis on reducing home energy usage.

We've all heard that well-placed landscaping can reduce cooling bills in summer and heating bills in winter; this book provides the information needed to put theory into practice. The authors present separate chapters dealing with the specific characteristics, problems and appropriate plants of four climate areas: cool, hot and arid, hot and humid, and temperate.

Additional chapters discuss natural lawn care, water-efficient landscaping, non-toxic pest management and the use of native plants.

The book is available in bookstores or can be ordered directly from the publisher ($19.95 postpaid). Write to Appropriate Solutions Press, Dover Road Box 39, Dept. FG, South Newfane, VT 05351; or call 802-348-7441.