The surest way to figure out whether a pine forest is infested with bark beetles is to wait for the trees to start dying.

The drawback - and it's a big one - is that you're left with a lot of dead trees, scarring a national forest or spoiling a timber harvest. Bark beetles have killed more than 70 million pine trees in Arizona and New Mexico since 2001, wiping out some stands of piñon and ponderosa.

Two college students think they've found a better, more efficient way to detect infestation. Zack Parisa, a forestry major at Mississippi State University, and Evan Thomas, a materials engineering major at Arizona State University, have invented a beetle-detection device that can identify nests of beetles before the insects mature, swarm and invade healthy, neighboring trees. Forest managers then could cut down the infected tree and potentially remove the threat.

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The device, developed with the help of an ASU entrepreneurial program, could help protect forests from destructive beetle attacks, prevent wildfires that feed on dead trees and let logging companies work more efficiently.

Currently, forest biologists rely on a mix of aerial surveys and legwork to find and track beetles. The aerial surveys are expensive, infrequent and reveal only how many trees are dead or dying. Biologists also tromp through forests to conduct beetle counts, using traps to estimate the insects' numbers, but those results help little in quashing attacks.

"Insects are becoming more troubling to land managers," said Parisa, who began toying with the idea for the detection device while working in an Alabama forest the summer after he finished high school. "We see what we do as a service industry. We think it could be beneficial for a lot of people."

The device, still in testing stages, turns the beetles' own natural communication methods against them, tracking the pheromones the insects use to attract one another. High levels of the pheromones lead to the nests where beetle larvae spend the winter. Left undetected, the beetles would swarm come spring and kill hundreds of trees in every direction. If the nest trees are removed before then, the attack is thwarted.

In tests, the inventors have been able to zero in on a single tree and cut the time needed to analyze data from three days to about two hours.

Parisa, 22, didn't set out to invent a beetle detector, but he started thinking about the problem while doing location work in Alabama's northwestern pine forests, which have been hit by beetle infestations in recent years. The only way to track the beetles was to watch for dying trees. Even then, options were limited, insecticides impractical.

"They move entirely too fast in the summer months to do anything," Parisa said. In the winter, meanwhile, beetles dump high concentrations of pheromones to find each other. Once they do, infestation rates climb quickly, "but they don't move as fast."

As he understood more, "I saw an opportunity and started to work on the problem," Parisa said. "There's not much else to do in Double Springs, Alabama."

He started working with best friend Thomas, 21, who began providing some of the engineering and mathematical expertise Parisa lacked. Although the two took separate educational paths, they kept working on the detection device.

They got a needed boost when Thomas discovered ASU's Edson Student Entrepreneur Initiative, which offers grants of up to $20,000 to help students launch business ventures. Parisa and Thomas were awarded the full grant, which helped clear the way to finishing prototypes.

"There's only so much you can do when you're using loaner equipment from the universities," Thomas said.

Parisa and Thomas have tested their detectors in the field, mostly in the pine forests of Mississippi and Alabama. They've learned which pieces of the often-delicate equipment travel well and which don't. They also have improvised along the way, finding new uses for existing devices.

They recently applied for patents and have submitted a paper for peer review and publication. With that sort of validity, "we can go out and work on projects and get more work," Thomas said.

With paid customers, they could draw a better picture of the long-term cost to build more devices and learn about whether the detection system could be used on a larger scale. They see their potential market as a mix of land and forest-management agencies and timber companies. Both groups have an interest in protecting trees from infestations, interests that Parisa says aren't as divergent as some think.

"The ability of a tree plantation to produce timber reliably can free up other lands for conservation," he said. "By managing the lands wisely, you can reach that balance."