Into the Garden: My son's search for spreading species
CHARLESTON, W.Va. -- "John, please help me weed."
"Mom, I hate to weed. Why do we have all of these flowerbeds? Why don't you just let the weeds take over?"
"John, please pull the vines from the trees along the edge of the woods and use the weed eater to cut them very close to the ground to try to kill them."
"Mom, I hate to pull vines and run the weed eater. Why do we care if they are in the trees? Why don't you just let those vines take over?"
Typical conversation. Every summer. Without fail.
Then came the summer of 2011. My son John, a wildlife biology major at Auburn University, researched summer jobs online and found something interesting with the West Virginia Department of Agriculture. He called from school in Alabama to tell me he landed a job as a "weed field scout," and he would be traveling across the state in search of weeds.
He went to work for David A. Dick, agricultural weed specialist, Plant Industries, Agricultural Pest Survey Programs Unit of the state Department of Agriculture. He received training, and then they equipped him (and several other weed field scouts) with a GPS, a mini computer with satellite internet connection, a camera and field gear -- plastic flash cards, papers, etc., with descriptions and photos of various invasive species.
Dick was kind enough to allow me to keep one of the flashcard flipcharts, produced by the U.S. Department of Agriculture. It's a wealth of information about invasive plants.
So from the ag department's hilltop community in Guthrie, John set forth to find weeds. The irony was not lost on me. But his enthusiasm was exciting, and he immersed himself into the project, traveling to the hinterlands to collect data for the Animal and Plant Health Inspection Service database.
The service is a multifaceted agency with a broad mission area that includes protecting and promoting U.S. agricultural health, regulating genetically engineered organisms, administering the Animal Welfare Act and carrying out wildlife damage management activities. This supports the overall mission of the USDA, which is to protect and promote food, agriculture, natural resources and related issues.
Each of the summer data collectors was assigned to different counties. They focused on public access points and roadsides as well as private land, John said. They went in search of mile-a-minute, Japanese honeysuckle, Japanese knotweed, common crupina, tree of heaven, multiflora rose, purple loostrife and more.
"If the species was on the hot list that we were targeting, we were looking for it. For example, if we found mile-a-minute, that was a bonus," John explained. "We were trying to locate and to get a feel for the invasion rate, the habitat, how big the site was and what environment the plants were living in. One year a certain site might be a mud hole, and the next summer it might be dried up. Habitats can change."
Checking to see if the invasives grow in changing environments was only one part of the job.
Later in the summer, John was asked to check on sites where biocontrols were being used to contain mile-a-minute.
"It's along the Potomac, the Ohio [rivers], in Tyler and Wood counties. It's typically within 100 yards of the river. But it's even in Kanawha -- at the Big Chimney exit, it's in someone's yard," he said. He saw it along power line sites.
"Power trucks probably brought it in. It can be anywhere, and it can be transported by log trucks, too. Anytime you move mud, wood, plant matter, it spreads an invasive species. It can spread other plants that might not be invasive in their native area but can cause damage to native plants and fauna in another area."
John said, "It can be something as common as honeysuckle. Essentially, a lot of times, it's a natural plant that's taking over -- that plant's fighting for survival.
He pointed to our neighbor's yard where they had lost several large oak trees recently, many because they were covered with ivy. "English ivy can be an invasive plant species, even though people plant it in their gardens."
According to Dick, there is an effort to contain the mile-a-minute using a weevil, the Rhinoncomimus latipes.
"The adults feed on the leaves and lay eggs on the leaves," Dick said. "Once the eggs hatch, the larvae bore into the stem of the mile-a-minute plants and feed. They then bore out of the stem, drop to the soil and pupate. The larvae actually cause most of the damage, killing the portion of the plant above where the larva bore out of the stem."
Dick said he usually releases 250 to 1,000 weevils at a site, depending on the size of the site and proximity of other release sites. After the weevils are released, field teams try to get back at least once a year to look for the presence of adult weevils, feeding damage, and/or stem node damage caused by larvae boring out of the stems. In addition, the cover of mile-a-minute within one mile of the release site is estimated.
The agency is cautious about the use of biocontrol agents.
"As far as what a modern biocontrol agent goes through before release, the testing is quite extensive," Dick said. "First, field teams go to the county in which the pest (mile-a-minute, in this case) is native. Then, they look for insects and pathogens that use that plant as a host in the native range.
"Then, these insects and pathogens are tested in caged trials inside the native county to see what else they feed on. If their feed range is too wide, the BC agent is rejected. If the BC agent has a sufficiently narrow host range, it will survive 'the cut,' and permits will be issued to import them into the U.S. under quarantine conditions for further testing.
"Once in the U.S., the BC agents are again tested in caged feeding trials to see what native plants or crops the BC agent might use as an alternate host. These tests are conducted with an eye toward both adult feeding and whether the BC agent can complete its life cycle on alternate hosts (i.e., will adults lay eggs, will eggs hatch, will the larvae feed on the alternate host, etc.). If a BC agent feeds on and completes its life cycle on plants other than the target, it will likely be rejected.
"Only BC agents that show a very high preference for a target plant will be considered for field trials. In the field trials, BC agents are released in fairly isolated areas to check for effectiveness in controlling the target plant. If a BC agent is shown to be highly host specific and at least somewhat effective, it will likely receive a permit to be reared and further releases can be made," Dick said.
One species on John's list was elusive.
"I never saw common crupina, nor has David Dick seen it in West Virginia," John said. While he was disappointed not to find the species as a scout, he knew it was a good thing that the weed wasn't invading West Virginia.
As one bumper sticker in the Agriculture Department's parking lot reads, "So many species, so little time."
Reach Sara Busse at firstname.lastname@example.org or 304-348-1249.