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GARDENING

Those little worms hanging from trees can be huge problem

If you saw a blizzard of identical little brown moths fluttering around your porch lights last December, you'd best call an arborist to come spray your trees now. They're a new pest and billions of their offspring will be hatching out any day. For years homeowners were told the inchworms eating their trees and dangling from silken skeins each May and June were native fall cankerworms, which experience a population crash after about three years. This may have consoled those facing a gauntlet of hanging caterpillars, arms raised to shield vulnerable areas such as eyes and coiffure, rather like Frodo battling his way through the webbing in that giant spider's lair.

But it wasn't cankerworm and it didn't go away. It kept coming back, and it kept spreading. It became a moth mystery. A caterpillar conundrum. In some South Shore areas, especially in Plymouth County, trees have been defoliated for eight springs in a row.

Then last winter, David L. Wagner, entomologist at the University of Connecticut at Storrs, positively identified the insects as something new here, the European winter moth (Operophtera brumata). So its population is probably not going to crash naturally, because it has no predators here.

"It has enormous potential for causing injury to landscape plants and trees and we are now faced with having to deal with it," said Bob Childs, entomologist with the UMass Extension's Landscape, Nursery and Urban Forestry Program. It prefers maple, crab apple, apple, blueberry, ash, and oak when young but will even eat geraniums when it gets larger.

Its only previous incursion into the United States was in the state of Washington, where introduction of its natural predator, a tachinid fly, brought winter moth numbers to acceptable levels. But the deliberate importation of a foreign insect has a time-consuming protocol that will take several years, as opposed to accidental importations, which happen with confounding ease and frequency, aided greatly by large, sealed, cargo containers used for international trade and sometimes packed with uninspected foreign organic matter for filler.

So spray away. But with what?

Two years ago Dominic Marini, retired regional fruit and vegetable specialist for UMass/Plymouth County Extension, lost his entire blueberry crop, a favorite of the winter moth caterpillar. But last spring's crop was fine after he sprayed his bushes with dormant oil in late April just as the buds were swelling, and again 10 days later in early May.

Dr. Donald Booth, entomologist for the Bartlett Tree Research Laboratory in North Carolina, recommends hiring an arborist to spray with Conserve CS. "It's registered for organic gardening and very effective, and you'll need an arborist with an hydraulic sprayer for big trees. The window for spraying is mid-April to mid-May."

Brian McMahon of Natural Tree & Lawn Care in Avon sprays clients' trees with dormant oil to smother egg masses before they hatch. He follows this up with two applications of Conserve SC, the commercial applicator version of Spinosad, at a one- or two-week interval beginning when buds start to open.

Organic Bulls-Eye Bioinsecticide and Monterey Garden Spray are Spinosad products for the homeowner that work well on caterpillars of all types, said Childs. They can be bought at local garden centers and some retail nurseries. "You can also spray something like B.t. (Bacillus thuringiensis) soon after the foliage has emerged. Spinosad is derived from a bacterium put through a fermentation process, while B.t. IS a bacterium. They're not bad for the environment."

Winter moths have a complex life cycle that allows them to afflict people in two completely different ways. After the eggs hatch in early April, the tiny caterpillars weasel their way into leaf and flower buds, eating them from the inside so that the buds open in tatters.

After bud break they become "free feeders," often dropping out of trees to sample flowers and bushes below. In early to mid-June they stop gorging and begin pupating in tiny cocoons just under the soil surface. After Thanksgiving they emerge as adult moths. Only the tiny males have wings. They swarm lights in early evening, their brown wings briefly giving front doors the appearance of having been smeared with sludge.

When you see them in large numbers, you know your garden will be assaulted the following May. That's because the flightless female moths scurry to the nearest tree and start climbing rapidly, while emitting a phermone, or scent, that attracts those winged males.

"She's a chubby little gray insect with vestigial half-wings and she runs up a tree," said Deborah Swanson, extension educator for Plymouth County/UMass Extension. "She goes pretty quick, and the males come and mate with her. She's headed for the top of the tree, laying eggs the whole way. She's on a mission." After producing eggs, the moths die, mission accomplished.

Swanson, who helped call initial attention to the new insect, spent a few nights last winter collecting egg-laying females in her Hanson backyard for examination. "I was out there in the pouring rain with an umbrella one night when temperatures were 38 to 40 degrees. They're really tough. The maple tree in my yard had so many moths on it, the bark looked like living fur." A few weeks later, the weakened 40-foot red maple split open in a snowstorm.

If people choose not to spray and their trees become defoliated, make sure to water them whenever there's a week without rain, said Swanson. "If they've lost their leaves, they'll put out a second set, but they need extra water to push those leaves out." Don't fertilize. That can further weaken the tree.

Winter moth is easily confused with fall cankerworm and bruce spanworm. In fact, the South Shore infestation did start with fall cankerworms, but then the winter moths took over. "We don't know the range of winter moth," said Childs. "It appears to be fairly coastal. It's south to the elbow of the Cape at Chatham, and it's up around the Boston area." Winter moth is a big deal, said Childs. "It's a new and permanent problem."

Pretty in pink: Roses were Abigail Adams's favorite flower, according to Connie Nielsen, president of the Weymouth Garden Club. So the group commissioned a new pink-toned rose in honor of Weymouth's most famous native daughter, a woman who churned her own butter, wrote wise letters of counsel to her husband, John Adams, who became the second American President, and her son, sixth President, John Quincy Adams. Some of the 4-by-3-foot disease-resistant shrubs will be used to landscape her birthplace, a modest cottage on East Street in Weymouth, near The Village Green maintained by the garden club. The Abigail Adams Rose was bred by Ashdown Roses of North Carolina and paid for with the proceeds of the club's bake sales, plant sales, and a flea market. Weymouth Mayor David M. Madden is scheduled to attend a Saturday luncheon at the Church of the Nazarene to introduce the rose, which can be ordered in gallon containers for $20 from club members (781-331-5685) to support their beautification work.

Gardner vines: After months of tending and training, the nasturtiums were installed this week at the Isabella Stewart Gardner Museum interior courtyard, an annual spring tradition that Gardner herself began 101 years ago. The 20-foot vines of orange flowers will cascade from the museum's third-floor balconies through April. A 1919 painting by Arthur Pope of nasturtium vines hanging in the courtyard is also on view.

Lecture on trees: Gary Koller will lecture about "Trees with Variegated and Colorful Foliage" today at 7 p.m. at Blithewold Arboretum, 101 Ferry Road, Bristol, R.I. Arboretum horticulturist Gail Read will discuss "The Life and Times of Blithewold's North Garden" Tuesday at 6:30 p.m. (Lectures are $12; 401-253-2707 ext. 16; www.blithewold.org.)

Flower show: The Salem Garden Club will hold a free flower show, "Treasurer's Abloom," at Old Town Hall, 32 Derby Square, this Saturday, noon-4 p.m. Call 978-745-0043 for more information.

Cactus show: The 21st Annual Connecticut Cactus and Succulent Society Show and Sale will be Saturday 10 a.m.-5 p.m. and Sunday 10 a.m.-4 p.m., free, at the Naugatuck Valley Community College Art and Music Center, 750 Chase Parkway, Waterbury, Conn. Free plants will be given to the first 50 families on both days and there will be a series of lectures. Follow signs from Exit 18 off I-84, call 860-489-8356, or visit www.ctcactusclub.com.

Fashion sense: In celebration of its 75th anniversary, the Beacon Hill Garden Club is sponsoring a small flower show called Flowers in Fashion at The Church of the Advent at 30 Brimmer St., Boston, open free to the public, Friday, April 16, 10 a.m.-4 p.m. The public is invited to enter in the photography, horticulture, and jewelry categories. (The jewelry category is a faux broach made from plant material). The Beacon Hill Garden Club's famous Hidden Gardens of Beacon Hill garden tour will be held Thursday, May 20, 9 a.m.-5 p.m. Tickets will be $30. Call 617-227-4392 or visit www.beaconhillgardenclub.org for information on either event. To buy in advance by mail ($25), send a self-addressed, stamped envelope with check to: BHGC 2004 Tour, Charles Street Station, Box 302, Boston, MA 02114.

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