Scientists link invasive barberry to Lyme disease
Lyme - Friday morning, off a shady wet trail in the town that gave Lyme disease its name, a man with a 30-pound propane tank and a flame-throwing wand showed a group from local land trusts how a bit of fire in the right spots can make their woodlands healthier for both native wildlife and humans.
"You want to heat it until the stem glows. Then it's dead," said Jeffrey Ward, chief scientist at the Connecticut Agricultural Experiment Station's Department of Forestry and Agriculture. He talked over the loud gush of the propane torch as he wielded it on a patch of thorny green branches springing from the forest floor in the Eno Preserve, owned by the Lyme Land Conservation Trust.
Ward's demonstration, for representatives of Lyme, Salem and East Haddam land trusts and the Nature Conservancy, is the outreach part of five years of research he and fellow experiment station scientist Scott Williams have been doing on the relationship between Japanese barberry, ticks that carry Lyme disease and deer overpopulation.
A highly invasive plant that forms dense canopies in forests - particularly those with high deer populations that eat most every other plant - Japanese barberry also creates moist, cool shelters that harbor ticks that carry the Lyme disease bacteria, Ward's and Williams' research has shown. Hot, dry conditions suppress tick populations.
At 28 study areas, including a parcel along Lord's Cove in Old Lyme, the two have been studying various aspects of the triangular relationship between ticks, deer and barberry, and spreading their message to land conservation organizations about the best methods for ridding forests of barberry. Deer serve as hosts for adult ticks, while the barberry functions as a nursery for ticks in their juvenile stages.
"How fitting, here we are in Lyme," said Ward during a presentation at the Lyme fire station before the torching demonstration, referring to the story of how Lyme disease was first identified in the 1970s from a cluster of cases in that town. Last year, there were an estimated 3,068 cases of the illness in Connecticut, causing victims a range of symptoms from flu-like fever, chills, headache and muscle aches to more serious nerve damage and arthritis.
During the presentation, Williams said tick abundance in barberry-infested areas is 67 percent higher than those where native plants are predominant. Also, the percentage of ticks that carry the Lyme bacteria is higher - 126 infected ticks per acre versus 10 per acre in barberry-free areas, Williams said, though the reason for that is as yet unclear. After barberry removal, Ward said, tick populations drop as much as 80 percent.
He stressed that they're not advocating for barberry removal just because it's non-native.
"It's not just an esoteric thing," he said. "It depresses wildflowers and native trees, and by controlling barberry you can have a real impact on human health."
Reservoirs surrounded by dense barberry also have diminished water quality, he said, because the local ecosystem it creates promotes more soil erosion than areas with more native trees and shrubs.
With red berries in the fall and small oval leaves in green, red or purple, the shrub was introduced to this country as a landscaping plant more than 100 years ago. It was often planted as a hedge to cordon off properties, its thorny branches forming an effective natural fence. The berries, a popular food for birds, deer and small animals, hold seeds that are rapidly spread in animal waste.
Bob Heffernan, executive director of the Connecticut Green Industry Council, said barberry continues to be popular, accounting for $4.9 million in sales in 2004. Despite that, the council, which represents landscapers, plant sales companies and related businesses, last year began a voluntary phase-out on sales of 25 varieties of barberry that research had shown to be the most highly prolific and invasive. The most common variety found growing wild in woodlands, with green leaves, was among them. The research to identify the 25 types, conducted at the University of Connecticut, was commissioned by the council.
Heffernan noted that despite the voluntary phase out in-state, which gives businesses until June 30, 2013, to get rid of remaining inventory, new invasive barberry plants continue to come into Connecticut when residents and businesses order them from out-of-state mail-order suppliers.
The voluntary phase-out, he said, was enacted because of barberry's highly invasive properties, but its role as a host for tick populations provides added motivation.
What should homeowners with a barberry bush or two in their yard do? Ward said he doesn't think removing it is necessary, although there are preferable non-native shrubs such as bayberry, highbush blueberry and winterberry.
"There are so many barberry in most forests, and they produce so many seeds, that removing the couple of plants in your yard is more symbolic than effective, sort of like using your finger to plug a leak in a dike," he said. "Time, energy and money would be better spent first controlling barberry infestations in the woods and along trails."
But for land conservation groups, with limited budgets and labor pools composed mostly of volunteers, tackling this persistent invasive shrub is a major challenge.
David Gumbart, assistant director of land management for the Nature Conservancy's Connecticut chapter, said barberry can be found on nearly all of the organization's 64 properties in the state. The conservancy has begun a program to determine the areas most in need of removal and, over the past two years, worked with the Lyme Land Conservation Trust on a pilot project at two properties.
Linda Bireley, executive assistant for the Lyme trust, said her group recognizes it as a key part of its land management responsibilities.
"Every one of our properties has some barberry somewhere," she said. Management plans being developed for each of its nine sites will include barberry removal, she said.
In Salem, the land trust has been working with a Natural Resources Conservation Service grant to get rid of barberry from the Walden Preserve, said Mark LaCasse, steward for the land trust.
A crucial part of scientists' Ward and Williams' work has been finding the most effective and economical ways to win the war against barberry, and spreading the word in workshops that include safety talks and demonstrations. That's where the propane tank and torch come in. For setup of tank, torch, backpack and safety equipment, land trusts should expect to spent about $300, he said.
Removal is a two-step process, they said, beginning with mechanical cutting with a brush saw or, in some cases, tearing up dense clusters with a small bulldozer. That is followed by selective application of herbicides or burning - a more labor intensive alternative, but preferred around wetlands, streams and other sensitive areas. After initial eradication, land managers should return with crews every year or so to prevent regrowth. In some places, there is so much of the prickly plant that the problem becomes figuring out where to begin, Ward said.
"Start along a trail, do a section 50 feet wide along the trail, then go back and widen it," he advised. "You'll get a sense of accomplishment, and it reduces the risk of Lyme disease for you and your pets."
During the demonstration, Ward pointed out one of the aspects of barberry's growing habits that's crucial for would-be barberry conquerors to understand.
"See where this branch touches the ground? That's how it creeps across the landscape, like fungus," he said, directing flame at the point where the branch disappeared into the leaf litter, as sparks flew into the damp air.
A good year, if you're a tick
By all indications, there will be a higher-than-normal tick population this summer.
So says Kirby Stafford, state entomologist at the Connecticut Agricultural Experiment Station. Based on a preliminary look at the first batch of samples collected last week, he said, it appears as though numbers of both black-legged ticks that can carry Lyme disease and dog ticks will be up a bit over average years, a point people should be aware of as they spend more time outdoors in the summer months.
"Anecdotally, we're getting a lot of ticks coming in for testing, and people are telling me they've been picking up a lot of ticks," Stafford said Friday.
The cool, wet spring, he said, was good for tick nymphs, an estimated 24 percent of which carry the Lyme bacteria. During hot, dry weather, tick populations decline.
"Any time there's a lot of humidity, it's beneficial for tick survival," Stafford said. The snowy winter, he added, probably had no impact - or even a positive one - on tick populations.
Black-legged ticks will bite humans at any stage of their growth, while dog ticks only bite humans in their adult stage.
- Judy Benson
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