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Bug Off! Researchers Use Photonics to Help Save Trees

Insect Infestation Spreading Across US, Canada

UMass Lowell Image
A close-up view of the invasive emerald ash borer. The adult beetle measures about a half inch long.

By Edwin L. Aguirre

A team of UMass Lowell researchers led by Physics Prof. Jayant Kumar is using photonics, or light technology, to mimic the color of a nasty beetle — the emerald ash borer (EAB) — which has already killed tens of millions of ash trees across more than a dozen states in the U.S. and two provinces in Canada.

“Many insects, including butterflies, exhibit color due to micro/nano structures on their wings,” says Kumar, who directs UMass Lowell’s Center for Advanced Materials. “In the case of this beetle, its color is bright iridescent green and serves as an initial mating signal to the male. The idea is to have artificial beetle decoys that simulate the color to attract the males. Hopefully, this will give us an idea of the level of infestation in an affected area so we can take appropriate action to save the trees.”

He says their collaborators at Penn State University, which is funding the project, will fabricate the decoys and deploy them in the field.

A Growing Problem From an Uninvited Guest

The emerald ash borer (PDF) (scientific name: Agrilus planipennis) is native to Asia. It was accidentally introduced into North America sometime in the 1990s, most likely through wooden crates and packing materials used in shipping cargo from overseas.

The EAB is now considered to be one of the most destructive invasive insects in the United States. According to the U.S. Forest Service, the first reported die-offs of ash trees occurred in the areas of Detroit, Mich., and Windsor, Ontario, in 2002. Since then, infestations have been found in Illinois, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, Wisconsin and Quebec.

The female lays its eggs on the bark of the tree’s trunk and branches. The eggs hatch into tiny larvae, which then bore through the bark and into the wood. As they feed, the larvae create a network of tunnels under the bark, disrupting the tree’s ability to absorb water and essential nutrients. The trees gradually weaken and die, with heavy, falling branches posing a great risk to people as well as to homes, buildings, cars and other properties. Millions of dollars are being spent in destroying infested trees, replacing them and using chemical and biological agents to control the spread of EAB.

Taking a Cue from Nature

Kumar and his team use polymeric Bragg gratings to mimic the color of the EAB beetle. 

“These gratings are periodic structures fabricated using polymeric materials that reflect a particular wavelength (color) of light and transmit all others,” says team member Mahesh Narkhede, a Ph.D. student in plastics engineering. “This is achieved by creating periodic variation in the refractive indices using two different polymeric materials. The gratings reflect the bright metallic green color of the beetle.”  

The grating can be produced at a high rate and low cost, and the resulting color matches those of the EAB with great accuracy, says Narkhede.

“The materials used are highly flexible, so they can easily be shaped into decoy beetles,” he says.