Читать книгу Maple Sugaring - David K. Leff - Страница 10

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The End of Maple?

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KILLERS ARE ON THE LOOSE. Invading aliens are attacking the old industrial city of Worcester, Massachusetts, and surrounding towns. Almost thirty-four thousand street and yard trees in 110 square miles, largely maples, have disappeared. An additional fourteen hundred acres of forested land have been stripped of maples, birches, and elms. Entire residential neighborhoods are practically denuded, leaving barren streets and unshaded homes. The invaders have coal-black bodies stippled with white spots, six bluish feet, and striped antennae that can be more than twice their body length. Fearsome-looking creatures, they are fortunately no more than an inch and a quarter long.

It sounds like a science fiction plot from some Hollywood B movie requiring a superhero’s intervention. But there’s no unspeakable horror threatening from outer space, and the courageous champion fighting this calamity is neither more powerful than a locomotive nor leaps tall buildings at a single bound. He’s a soft-spoken entomologist with a beard and ponytail who wears jeans and work boots.

If you think the mundane terrestrial origins of this animal or its diminutive size is reason not to fear the end of maple trees in our region, then you probably are not aware that the American chestnut was once a dominant forest tree throughout most of New England, used for everything from fence rails to pianos and utility poles, until a blight caused by nearly invisible fungal spores imported from Asia wiped out almost all of them in little more than a generation. Persistent stump sprouters, these woodland giants are now just an occasional large shrub. Look at some old postcards and marvel at the colonnades of grand elms that once graced the avenues of almost every town and city in the Northeast and Midwest until Dutch elm disease made quick work of them, leaving once-leafy neighborhoods as barren as the residential streets in the Greendale and Burncoat neighborhoods of Worcester are today.

So far, the Asian long-horned beetle (Anoplophora glabripennis), or ALB, as it is popularly known, has remained a scourge of urban areas because, as crossroads of international commerce, they are likely to receive nonnative invasive species as unwanted hitchhikers on pallets and in shipping containers delivered to the businesses clustered there. No commercial sugarbush has yet been affected, but ALB has been a hot topic at maple meetings and around evaporators for several years. If “established here, it could be one of the most destructive and costly invasive species ever to enter the United States,” according to the U.S. Department of Agriculture. The insect is capable of riddling a tree with three-eighths-inch borings, about a taphole’s diameter, and not only compromise its vascular system, but weaken its structural integrity so severely that the trees fall apart and simply collapse. Uncontrolled, ALB could quickly spread to sugar orchards and put an end to syrup production. ALB kills trees. It could kill an entire food industry.

With piercing blue eyes, a marquee-quality name, and a fierce determination to fulfill a mission, Clint McFarland is one of the Worcester area’s leading antagonists of ALB. He works for USDA’S Animal and Plant Health Inspection Service—better known by its acronym APHIS—as project director of ALB eradication. On a snow-frosted January day we met at his office, a sprawling single-story structure on the outskirts of downtown. He escorted me to a small room among a warren of crowded cubicles. The tight space was busy with cabinets, a couple of desks, computer terminals, and teetering piles of paper. A soft-voiced man of energetic enthusiasm preaching a gospel of awareness, he was eager for me to meet the beetles, because a heads-up public was the best weapon against spread of the scourge.

Often citizens are the first to find new infestations, like the woman who discovered the insects in her yard and worried that they might bite or sting her grandchildren. Tracking down an image of ALB with a few keystrokes on her computer, she discovered that government authorities were interested in sightings. Within twelve hours, a SWAT team of bug hunters was in her yard taking down the trees.

Keen to have me know his nemesis in all its manifestations, McFarland gathered illustrations, vials, bags, mounted specimens, chunks of wood, and other show-and-tell objects from around the room, explaining each in exact detail, like an athlete or hunter showing off his trophies. Onto the table in front of me he tossed a thick branch perforated with the telltale exit holes of newly emerged adults and the roundish pockmarks carved into the bark where females had chewed nest spots to lay eggs. He had a round latitudinal slice of tree trunk, called a cookie, with a network of cavities and tunnels burrowed by the insects. He showed me the white, pill-shaped eggs, the wormlike off-white larva and pupa, and the glossy-black, white-stippled adults with their widespread antennae. Perfectly still and entombed in a jar, the beetle appeared elegant in its symmetry and simple coloring, though a living one crawling around would have given me the creeps.

McFarland plopped a couple of containers onto the table. Inside appeared to be sawdust. “Frass,” he said—a mixture of gnawed wood and bug poop that developing larvae push onto the ground or nearby limbs as they burrow inside a tree. It’s one of the telltale signs of ALB, produced during the larval stage when the insects gnaw deep into heartwood to feed on nutrients and carve their network of tunnels. I thought frass might be McFarland’s ultimate piece of ALB evidence, but he carefully placed a two-foot-tall log in front of me. It had been cut in quarters the long way and then hinged so that it opened to display interior ALB carvings, intricate lacunae of oval and linear excavations that left the branch a hollowed shell.

Soon we were in a small, dark car with government plates, prowling a predominately single-family middle-class neighborhood barren of trees except for a few spindly saplings at roadside. It had the stark vibe of a fresh subdivision carved into cropland, though the houses had been occupied for at least a couple of generations. McFarland sighed as he showed me photographs taken before the infestation. It had been a handsome street of overarching, mature shade trees. As in much of Worcester, red and Norway maples were common, and once infested they had to come down. They had been replaced by ALB-resistant oaks and other seedlings, but it would be years before those trees cast substantial shadows on the pavement and homes. These new plantings were among tens of thousands being established, including spruce and other evergreens, dogwood and crab apple—signs of perseverance and hope that ALB eradication efforts will not leave these areas naked. Still, the neighborhoods will never look the same without their colorful fall maples, showy spring horse-chestnut flowers, and white birch trunks.

A native of Asia, ALB landed in this country hidden in pallets and shipping crates from the Far East. No one knows when it arrived, but it was first discovered in 1996 in the Greenpoint area of Brooklyn, New York. Since then, it has been found in other nearby areas of New York, the northern New Jersey suburbs, and in and around Chicago. Although ALB was officially declared eradicated in Chicago and parts of New Jersey by 2008 (the same year the Worcester beetles were discovered), a new infestation was found in 2011 in southern Ohio not far from Cincinnati. An infestation in Boston and Brookline that covered ten square miles was declared eradicated in 2014. In addition to maples, ALB attacks elms, willows, birches, ash, and horse chestnut, some of our most commonly planted and beautiful trees found in yards and along streets, as well as in the woods. In all, there are thirteen genera victimized by ALB.

Our next stop was a subdivision that looked like it was built toward the end of the last century. There weren’t many large trees in front of the houses, but the yards backed up to scraggly woods where kids played and leaves were tossed in fall. Dozens of these trees, ranging from pole timber to about eighteen inches in diameter, had a string of orange surveyor’s tape wrapped around them, mark of a death sentence. McFarland handed me his field glasses, and with his guidance it became easy to see trunks and branches riddled with adult exit holes and the oval bark pits, like scars, where the females had nested. I spotted uneven lumps of frass in the crotch of several branches, as if someone had been sawing into the limbs above.

With binoculars usually around his neck, McFarland might be mistaken for a bird watcher as he lifts them to peer into branches high overhead. He’s a lookout. Like a military scout, he’s always on watch, ready to detect the slightest sign of the enemy. It’s a big job, with millions of trees to keep an eye on, which is why he needs his posse of public eyeballs. In addition to the signs I could see through the lenses or actual sightings of adult insects, he looks for unseasonable leaf yellowing, broken or dying branches, and sap flows caused by excavation wounds.

Trees infested with Asian long-horned beetle marked for cutting

The beetles are active in summer and early autumn, when a mated female might chew between thirty-five and ninety depressions in the bark, in each one laying an egg that hatches in about ten days to two weeks. The emerging caterpillar burrows through the bark and into the layer of the tree where sap flows, then into the woody tissue to develop and overwinter. In spring, the beetle larvae build a hard case and develop into adults, chewing their way out in summer and leaving those perfectly round exit holes, often with frass beneath them. Adults feed on small twigs and leaves, mate, and die with the advent of cold weather.