After 30 years of helping to turn Riverton Borough into a wonderland of shade trees, Barry Emens still grows and guards his creation.

"This is a white ash in trouble," he said one morning last week, pointing through his windshield as he turned from Second Street onto Linden Avenue.

Crickets were chirping in the muggy heat as Emens, chairman of the borough's shade tree board, parked his SUV.

He pulled a long pole from the truck and strode toward a scraggly, nearly barren tree on the southeast corner.

"OK, what have we got here?" he mused as he hoisted his pole toward a three-sided purple rectangle hanging from a low branch, and brought it down.

It was, he explained, an insect trap that will tell him if this mile-square Burlington County borough is yet home to the devastating beetle known as the emerald ash borer.

'Tremendous damage'

Since 2007 these half-inch borers have been found in 27 states, including in Bergen, Burlington, Mercer, Middlesex, Monmouth, and Somerset Counties in New Jersey. In Pennsylvania they have appeared in 61 counties including this month in Lehigh County and last month in Philadelphia.

"It's estimated they will cause $10 billion in damage in the U.S. by 2019," said Paul Kurtz, a senior entomologist with the New Jersey Department of Agriculture.

Most invaded states, including New Jersey and Pennsylvania, have created task forces to monitor and combat the threat. But in Riverton the job falls largely to this white-haired, sunburned volunteer who on this day was making his rounds in tan Bermuda shorts and a polo shirt.

"They're doing tremendous damage in the northern part of the state," Emens, 72, said of the ash borer as he inspected the walls of the trap. "It's not a matter of if they get here but when."

About 3 feet tall and 16 inches wide, each exterior wall of the trap is coated with a glue that holds any winged insect that touches it.

A pad inside, baited with a pheromone, should lure nearby borers to the sticky walls, dotted on this day with dozens of little critters - a few still squirming.

"Well, I don't know," he said, crouching close. "I haven't seen any yet." He peered at four half-inch beetles stuck to one panel. "These little guys are green," he mused, "but not metallic green."

And after a minute's study he concluded that none were emerald ash borers, and hung the trap back in the tree. At week's end he will send them to a state lab for inspection, but for now he is relieved.

While Moorestown, four miles to the east, and Edgewater Park, 10 miles north, have seen emerald ash borers this year, the two traps Emens set in Riverton a few weeks ago have so far shown none.

"But I think it's only a matter of time," he said, "so we have to be ready." Seventy-one ash trees line this town's streets and town park, he said, and many homeowners have them on their properties.

If an invasion comes, it will cost about $100 a year to protect each tree with larvicide injections, "but it's worth it."

For 42 years Emens, who grew up in neighboring Palmyra, used his forestry degree from the University of New Hampshire as an agent of the U.S. Department of Agriculture, based in Trenton.

Among his proudest accomplishments, he said, was serving as director of the USDA's program to exterminate the longhorned beetle, a voracious destroyer of maples, willows, poplars, and ash.

His task force cut down 20,000 infected trees in and around Carteret and Woodbridge, he recalled. Environmental groups protested the scope of the measure, Emens said, "but it was like a cancer. It had to be done, and it worked. We stopped them."

Blown away

But protecting trees is one thing, he said. Selecting, placing, and maintaining trees is the aesthetic, satisfying upside of forestry. And Riverton, he added, "is a forester's dream."

Founded in 1865 by wealthy Philadelphians who built summer villas on the banks of the Delaware, Riverton's "founding fathers" wrote a master plan, Emens said, that called for wide streets with 7- to 12-foot-wide greenswards between the sidewalks and curbs, expressly for the planting of shade trees.

Gazing north up Second Street, Emens spotted an Amur maple. Strolling to it, he fingered several of the little pink seed pods, or samaras, hanging from its low branches.

"They call these 'ruby slippers,' " he said fondly, and then cast his glance up and down the street.

"This block just blows you away," he marveled, and insisted on taking a walking tour of it to show what the borough's romance with trees has produced.

'Doing great'

Heading north, he pointed across the street to a flowering peach, with its long, slender, glossy leaves, then overhead to an "Armstrong" red maple. "It's the right tree in the right place," he explained, "because it's columnar - it won't spread out - and it won't reach those telephone wires."

Continuing along, he pointed out a Green Mountain sugar maple that he chose because it's "specifically drought-tolerant. Look at those leaves!" he exclaimed. "How dark and green they are. This is the new kid on the block and it's doing great."

Turning around, he counted off 16 trees the borough had planted on this short block in recent years, with 14 of them different species.

Today Riverton is home to 151 tree species, according to Emens, including willow oak, dawn redwood, black gum, ginkgo, Princeton elm, river birch, crepe myrtle, and American beech.

Riverton's commitment to trees has won it recognition as a "Tree City" by the Arbor Day Foundation every year since 1988.

"Well, we go for diversity in a big way," he explained as he strolled the perimeter of the town park, pointing out an American elm planted in 1999, a golden locust from about 15 years ago, and the young Norway spruce that will serve as the borough's Christmas tree.

Diversity "looks so much better," he said. "And if something like Dutch elm disease or the emerald ash borer comes along, it doesn't wipe out half your trees."