Gregg Henderson, Bogren, Richard C.
NEW ORLEANS – Visitors to the Parkway Partners monthly plant sale Saturday (Aug. 11) purchased scores of vetiver grass plants to add to their landscapes.
For some, the plants will be purely ornamental, but for others, the grass will be planted to try to keep termites from invading their homes.
Planting vetiver grass as a termite barrier is part of a grassroots effort by Dr. Gregg Henderson to encourage people to use the plant as one of the tools to control Formosan subterranean termites.
Henderson, an urban entomologist with the LSU AgCenter and acknowledged expert on termites, 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.
He was invited to talk about his research in a presentation at Parkway Partners in conjunction with the organization’s monthly plant sale in New Orleans.
A 25-year-old private organization, Parkway Partners is a partnership of citizens and government officials for the maintenance and beautification of the New Orleans neutral grounds, playgrounds and parks, along with preserving the urban forest and other green spaces, according to Jean Fahr, executive director of the organization.
Fahr said the second Saturday program each month is designed to help people find plants to replant yards and gardens following Hurricane Katrina. Presentations like Henderson’s are given in conjunction with the types of plants offered. So with vetiver grass for sale this month, Henderson was a logical choice to invite.
"Our landscapes changed dramatically," Fahr said. "People have the opportunity to reevaluate their landscapes and make changes, and vetiver is one of many choices in landscapes."
Vetiver has been in the United States for about 200 years, Henderson said. In earlier times, people put vetiver roots in their closets and armoires to repel clothes moths. It also repels cockroaches, ants, ticks, weevils, nematodes and mole crickets as well as other insects.
Henderson first learned of the potential of vetiver grass as a termiticide about 13 years ago from Don Heumann, who was then a nursery and greenhouse operator in Metairie. Because he was aware of the growing damage termites were causing in the New Orleans area, Heumann thought he might have uncovered a possible solution to the termite problem when he noticed he had no bugs in his greenhouses where he was growing vetiver.
Heumann piqued Henderson’s interest and brought the LSU AgCenter researcher some vetiver plants to evaluate.
Widely known for its effectiveness in erosion and sediment control, vetiver grass is highly tolerant to extreme soil conditions and is often used to rehabilitate contaminated lands. The deep roots anchor the plant and hold soil together on hillsides and contours.
Vetiver, it turned out, is both a repellent and toxic to termites.
Henderson and a research team that included Dr. Roger Laine, a biochemist in the LSU AgCenter’s Department of Biological Sciences, and others first experimented with ground vetiver roots in sand.
They discovered termites avoided going through the sand when the sand was introduced into a termite colony. Their second experiment isolated compounds in the extracted oils from vetiver roots, and some of those compounds also repelled termites.
Henderson isolated several compounds from the vetiver oils and discovered a chemical called nootkatone was responsible for turning away termites. The substance also is found in Alaskan yellow cedar.
Since his earlier experiments, Henderson has been looking at vetiver grass to provide a combination of erosion control and termite repellent on grass levees.
Last year, with a grant from the U.S. Department of Agriculture’s Agricultural Research Service, Henderson planted vetiver grass at the LSU AgCenter’s Coastal Area Research Station at Port Sulfur to test the grass against Formosan subterranean termites.
"These experiments are meant to demonstrate that termites will stay away from food sources close to vetiver and are meant to demonstrate their potential for levee plantings," Henderson said at the time.
Throughout the world, termites have caused problems on levees by tunneling in the soil and weakening the integrity of the structures, Henderson said. He hopes to demonstrate that vetiver, which is widely known for its effectiveness in erosion and sediment control, will help keep subterranean termites from undermining levees in the United States.
One of the problems with levees in New Orleans has been the infestation of mature trees by Formosan subterranean termites, which not only undermine the levees but also feed on the trees, weakening them and contributing to their tendency to topple easily in high winds.
Henderson said he believes a major cause of levee breaks are subterranean termites. He said 70 percent of the seams of flood walls on the London Avenue canal, the site of levee breaches during Hurricane Katrina, showed signs of insect infestations – some surely were termites, but others could have been fire ants.
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 Hurricane Katrina in 2005. In addition, Henderson said experts believe the voids in the soil caused by termites eating away tree roots and the termite tunnels themselves served as "pipes" that allowed floodwaters to flow from the canals into the city.
Five large trees that were snapped near one of the London Avenue breaks had large Formosan subterranean termite nests. "This certainly would have led to a piping effect of the roots that clearly would have penetrated the levee and maybe even invaded the space in the wall," Henderson said.
"It’s almost certain termites contributed to the levees’ failure," he said.
Henderson said termites feeding on bagasse seams in the floodwalls in the New Orleans levees also are suspected of contributing to levee breaches.
Henderson’s current research is intended to supply the U.S. Army Corps of Engineers with information on how vetiver can be used to strengthen levees by both controlling Formosan subterranean termites and providing erosion control.
"I believe we should be using it on levees," Henderson told the audience at Parkway Partners. "That’s why I’m here today."