(Beyond Pesticides, August 30, 2007) Vetiver grass, a species native to India, may provide protection against two plagues facing recovery in New Orleans: termite infestations and floods, according to Dr. Gregg Henderson, Ph.D. Already known for its effectiveness in erosion and sediment control, vetiver is both a repellent and toxicant to termites, which cause an estimated $5 billion in structural damage per year in the U.S. The plant is highly tolerant to extreme soil conditions, which, along with its deep roots, make it ideal for rehabilitation of contaminated lands and holding soil together on hillsides and contours. However, Dr. Henderson, an urban entomologist with Louisiana State University’s AgCenter, is interested in what is inside vetiver’s roots, namely the chemical responsible for turning away termites, as well as cockroaches, ants, ticks, weevils, nematodes, mole crickets, and other insects.
His research team isolated several compounds from vetiver oils and determined that a chemical called nootkatone, is a repellent for Formosan subterranean termites. Dr. Henderson has been studying Formosan termites for years and is a strong advocate for taking advantage of the chemicals in vetiver grass to control the termites in many locations.
Throughout the world, termites have caused problems on levees by tunneling in the soil and weakening the integrity of the structures, Dr. Henderson said, including those that broke in New Orleans during Hurricane Katrina in 2005. “It’s almost certain termites contributed to the levees’ failure,” he said, noting that 70 percent of the seams of flood walls on the London Avenue canal, the site of breaches, showed signs of insect infestations.
Years before Katrina struck, Dr. Henderson cautioned that Formosan termites were undermining the protective system by eating the sugar-cane-based seam-filling material in the concrete dike walls and infesting mature trees along the levees. Experts suspect falling trees that pulled their roots out of the ground contributed to the weakening and eventual breaches of levees in New Orleans during Katrina. Planting vetiver grass, Dr. Henderson says, could not only provide erosion control and a breakwater barrier, but it could help prevent future damage by warding off termite infestations.
The U.S. Army Corps of Engineers, charged with fortifying the city’s levees, though is skeptical that the grass can really live up to all its touted potential. The Corps regards termite infestations as only “a minor contributing factor” to levee failures, and officials remain concerned that vetiver could prove to have downsides that outweigh it benefits.
Vetiver is native to India, and the Corps is concerned that the plant might prove to be an invasive species. Government officials are still wincing from the aftermath of importing virulent kudzu””known as “the vine that ate the South”””for erosion control in the 1930s, and Corps planners are concerned about vetiver’s tendency to develop roots at its leaf joints. The plant could root elsewhere if pieces broke off and washed away during a flood.
Vetiver advocates point to hundreds of years of cultivation abroad to prove that the grass is not an aggressive plant. The grass has been a part of the New Orleans landscape for two centuries without becoming invasive, say local residents. “I grew up knowing about vetiver,” said Jean Fahr, president of the civic gardening group Parkway Partners. “My grandmother hung it in her closet to repel moths.”
The Corps still thought enough of vetiver to include it in a short list of 10 plants they are considering for vegetation along the New Orleans levees. “It has some characteristics worth exploring,” concedes Col. Murray Starkel, in charge of operations at the Corps’ New Orleans district office.
Vetiver grass may prove to be an integral piece to revitalizing the region and find its use as a non-toxic structural control against termites in private homes nationwide as well.