By Adrian Higgins
A pear seedling selection named Bradford was cloned by the gazillion to become the ubiquitous street tree of America’s postwar suburban expansion. Then it turned invasive.
Carole Bergmann pulls her small parks department SUV into an aging 1980s subdivision in Germantown, Md., and takes me to the edge of an expansive meadow. A dense screen of charcoal-gray trees stands between the open ground and the backyards of several houses. The trees are callery pears, the escaped offspring of landscape specimens and street trees from the neighborhood. With no gardener to guide them, the spindly wildlings form an impenetrable thicket of dark twigs with three-inch thorns.
Bergmann, a field botanist for the Montgomery County Parks Department, extricates herself from the thicket and in the meadow shows me that what I take to be blades of grass are actually shoots of trees, mowed to a few inches high. There are countless thousands, hiding in plain sight in Great Seneca Stream Valley Park. If it were not cut back once a year, the meadow would become like the adjacent screen, wall upon wall, acre upon acre of black-limbed, armored trees worthy of Sleeping Beauty’s castle.
“You can’t mow this once and walk away,” said Bergmann, who began her 25-year career in the department as a forest ecologist but has been consumed by an ever-pressing need to address the escape of the Bradford pear and other variants of callery pear, a species that originated in China, along with other invasive exotics.
By Neil Shaw
JOHANNESBURG — One of the world’s largest urban forests is under threat from a tiny beetle.
The polyphagous shot hole borer is thought to have made its way to Johannesburg from Southeast Asia on packing crates or through the trade in plant materials.
Trudy Paap, a forest pathologist at the University of Pretoria, discovered the beetle in the Pietermaritzburg Botanical Gardens last year. She published her discovery in the journal Australasian Plant Pathology, calling it part of “the surge in the global spread of invasive forest pests” because of globalization.
The beetle has since moved to Johannesburg, 200 miles away, and spread across its urban forest, which according to the Massachusetts Institute of Technology initiative Treepedia has the world’s sixth-largest green canopy cover.
Today, many of Johannesburg’s estimated 6 to 10 million trees are dying, a crisis obscured only by the current winter season. Some of the infected trees have the telltale holes the 2-millimeter-long beetle makes in their bark.
“This beetle doesn’t actually eat the trees,” Paap said. Instead it carries a fungus that blocks the vessels that transport water and nutrients, “which ultimately leads to die-back and death of the tree.”
Though scientists don’t know just how many trees have died from the beetles’ invasion, the outlook for Johannesburg is grim: “The city is going to lose a lot of trees.”
The trees do not have an evolved resistance to the polyphagous shothole borer, unlike in Asia where the beetles naturally occur.
It is the older, more established trees that are at risk, said arborist Neil Hill. “So that’s going to leave a gap in the landscape. And if we don’t start to plant straight way with new trees that gap is going to become more and more of a concern as far as urban blight, pollution, aesthetic beauty.”
State and federal entomologists believed the destructive pest would show up near the New Hampshire border, not hundreds of miles to the north.
By Janet Marinelli
Edward O. Wilson clambered partway down a slope in the Florida Panhandle, aided by a park ranger and trailed by a few dozen scientists, conservationists, and local landowners. The group had gathered in Torreya State Park, a landscape of dazzling botanical diversity along the upper Apalachicola River, as part of a whirlwind two-day meeting early this month to ponder the fate of its most storied tree. As the wind gusted through leafless branches, the lanky, white-haired Wilson, at 88 years of age still one of the most brilliant biologists of his generation, planted a seedling of the Florida torreya, North America’s most endangered conifer.
Wilson first visited the Apalachicola bluffs in 1957, as a self-described “young guy” with a new position at Harvard University, on an ant-collecting trip in Florida. “I came here,” he recounted, “the way you would go to Paris to visit a cathedral. I just had to see the torreya.” The trees had already begun their steep decline.
More than 60 years later Wilson was back. This time he declared the site “is not only a cathedral, but also a battleground at which one of the greatest events in American history will take place” — a turning point, as he sees it, in the planetary struggle to slow biodiversity loss.
Last spring, another “young guy” was at Torreya State Park on a camping trip with his lab. University of Florida forest pathologist Jason Smith “couldn’t believe how much worse the torreyas were” than when he had seen them the year before. “The population was crashing.” Smith, who has reddish brown hair and a bundle of energy, decided to assemble a team to reflect on the meaning of the species’ imminent demise, to catalog the “torreya tree of life” — all living things with which it associates in the wild — and to plan a last-ditch effort to save it.
“This is a now or never moment for the species,” he says.
While the massive wildfires and tree die-offs out West have gotten most of the press in recent years, the Eastern forests are also in crisis. An increasing number of the region’s iconic native trees are plagued by pests and pathogens introduced from abroad. This has researchers scrambling to find genes that can help impart resistance, and to breed them into the ailing trees. Because classical crossbreeding takes decades — perhaps too long for a critically endangered species like the torreya — options once unimaginable as conservation measures are now being considered, including the new group of gene-editing technologies called CRISPR that has taken the biotech world by storm.
The growing forest health crisis is forcing scientists, conservationists, and the public to answer some of conservation biology’s thorniest questions. Will we be able to use biotechnologies on the frontier of plant science to rescue imperiled species? Should we? And when so many species are at risk, does it make sense to go to extraordinary lengths to save a tree like the Florida torreya that has a tiny historical range and no commercial value?
Insects, both beneficial and disruptive, have always been front-of-mind for the people growing our food. Of particular interest in today’s world are invasives: insects that are not native to a region and whose introduction (whether intentional or accidental) is likely to cause harm to our environment, our economy or human health. Or already has.
A 2016 report in Nature Communication estimates that the annual economic impact of invasive insects on goods and services in North America is at least $27.3 billion. And this, say the authors, is likely an underestimation because determining the economic impact of invasives can be particularly difficult. “Most cost estimates are disparate, regionally focused, cover variable periods and are not always grounded in verifiable data,” write the authors. Additionally, the spread and the impact of invasive insects is likely to increase in coming years due to climate change, rising human population densities and intensifying international trade. But, say the authors, there is a way to minimize the impact: increased surveillance, containment and public awareness. In other words: To protect our local farmers, food systems and economies, we – the general public – need to pay attention to the bugs around us.
Source: Beetles making difference in woolly adelgid fight at Nay Aug Park – The Times-Tribune, 2017-04-15
By David Singleton
A beetle is winning the battle against the hemlock woolly adelgid at Nay Aug Gorge.
Almost 20 years after the woolly adelgid arrived at Nay Aug Park and started threatening the hemlocks in and around the gorge, officials believe they’ve finally gained the upper hand against the invasive, tree-killing pest, thanks in large part to a predatory beetle called S. tsugae.
“I think we caught it in time, and we have turned the corner. There is no doubt about it,” city forester Tony Santoli said. “I have seen great improvement.”
Since it started working with Santoli in 2011, Tree-Savers, a private company with offices in Waymart that specializes in saving endangered hemlocks, has released about 10,000 S. tsugae beetles at Nay Aug as part of an effort to eradicate the woolly adelgid and restore the park’s weakened hemlocks to health.
Like the woolly adelgid, the beetle — its full scientific name is Sasajiscymnus tsugae — is native to Japan. It is the woolly adelgid’s natural enemy, feeding on the tiny insect’s eggs.
A beetle is winning the battle against the hemlock woolly adelgid at Nay Aug Gorge.
By Holly Ramer, Associated Press
They may be down but they’re not out: Damaging insects can emerge from fallen trees and logs for several years after a major storm, according to a U.S. Forest Service study that reinforces long-standing warnings against moving firewood from place to place.
Timber that gets blown down, broken or damaged by wind is often cut and used as firewood, which in turn can enable the spread of invasive, destructive insects that drain the life out of forests from New England to the West Coast.
Such pests are projected to put 63 percent of the country’s forest at risk through 2027 and carry a cost of several billion dollars annually in dead tree removal, declining property values and timber industry losses, according to the peer-reviewed study last year in Ecological Applications.
Researchers were surprised to find that wood harvested even three years after the tornado produced a significant number of insects.
By Deanna Weniger
The emerald ash borer has proved an elusive foe to conservationists. It hides in the tree tops and its larvae stow away under the bark of the ash tree, making early detection difficult.
Scientists have tried a host of methods — purple sticky boxes, yellow pan traps and bark stripping — in a desperate effort to stop the destruction of the invasive wood boring beetle that has killed tens of millions of ash trees in over 20 states.
While the beetle can hide from humans, it’s not as good at hiding from natural predators, such as the smoky-winged beetle bandit, also known as Cerceris fumipennis.
The University of Minnesota Extension office is looking for volunteers to locate and monitor these harmless wasps that build their nests in sandy soil.
Release by University of Exeter
Ash trees which can resist the killer dieback fungus may be more vulnerable to attacks by insects, according to new research.
Scientists from the universities of Exeter and Warwick examined trees which are resistant to ash dieback and – unexpectedly – found they had very low levels of chemicals which defend against insects.
With efforts under way to protect ash trees from dieback, the scientists warn that selecting trees for fungal resistance could put them at risk from insects.
Aside from ash dieback, the other major threat to European ash trees is the Emerald Ash Borer beetle, which has already devastated vast tracts of ash in the USA and is currently spreading westwards across Europe.
By Rowena Lindsay
Hemlock woolly adelgids aren’t native to North America, but droves of them have settled into American forests where they threaten entire ecosystems.
A tiny bug, no bigger than a grain of pepper, is wreaking big-time havoc in US forests, and forest managers are scrambling to keep up.
Hemlock woolly adelgids aren’t native to North America, but droves of them have taken up residence in hemlock forests, from New England to the West Coast, thanks to increased trade and travel. Nestled under the needles of hemlock trees, the invasive insects cut off nutrients to the tree and can eventually take down trees that have stood for 300 years.
If left unchecked, the hemlock woolly adelgid and other pests are projected to put 63 percent of the nation’s forests at risk by 2027, according to a study published this year in the journal Ecological Applications. The tiny invaders could put several species of hemlock at risk for extinction, threatening the biodiversity and stability of ecosystems across the country and cutting a carbon sink for mitigating greenhouse gas emissions.
Globalization has opened the door for hundreds of invasive pests, from the Asian longhorned beetle to the emerald ash borer. And climate change, it seems, will make it even more difficult to evict them.