By Rabiu O. Olatinwo, Stephen W. Fraedrich and Albert E. Mayfield III
In recent years, outbreaks of nonnative invasive insects and pathogens have caused significant levels of tree mortality and disturbance in various forest ecosystems throughout the United States. Laurel wilt, caused by the pathogen Raffaelea lauricola (T.C. Harr., Fraedrich and Aghayeva) and the primary vector, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff), is a nonnative pest-disease complex first reported in the southeastern United States in 2002. Since then, it has spread across eleven southeastern states to date, killing hundreds of millions of trees in the plant family Lauraceae. Here, we examine the impacts of laurel wilt on selected vulnerable Lauraceae in the United States and discuss management methods for limiting geographic expansion and reducing impact. Although about 13 species belonging to the Lauraceae are indigenous to the United States, the highly susceptible members of the family to laurel wilt are the large tree species including redbay (Persea borbonia (L.) Spreng) and sassafras (Sassafras albidum (Nutt.) Nees), with a significant economic impact on the commercial production of avocado (Persea americana Mill.), an important species native to Central America grown in the United States. Preventing new introductions and mitigating the impact of previously introduced nonnative species are critically important to decelerate losses of forest habitat, genetic diversity, and overall ecosystem value.
Hayes, Deborah C.; Kerns, Becky K.; Patel-Weynand, Toral; Finch, Deborah M. . 2021. Introduction. In: Poland, Therese M.; Patel-Weynand, Toral; Finch, Deborah M.; Ford Miniat, Chelcy; Hayes, Deborah C.; Lopez, Vanessa M., eds. Invasive Species in Forests and Rangelands of the United States: A Comprehensive Science Synthesis for the United States Forest Sector. Heidelberg, Germany: Springer International Publishing: 1-4. https://doi.org/10.1007/978-3-030-45367-1_1.
Invasive species are a historical, long-term, and continually growing threat to the ecology, economy, and infrastructure of the United States. Widely recognized as one of the most serious threats to the health, sustainability, and productivity of native ecosystems, invasive species issues have commonly been viewed as problems specific to Federal, State, and private landowners. However, it is increasingly apparent that the impacts from these species are all encompassing, affecting ecosystem processes in addition to the economics of land management, public and private infrastructure, the energy sector, international trade, cultural practices, and many other sectors in the United States.
By Peter Fimrite
It is the forgotten killer when compared to our increasingly frequent climate calamities, but the virulent pathogen known as sudden oak death remains active and is spreading death so fast it could destroy California’s coastal forest ecosystem, UC Berkeley scientists reported Thursday.
The deadly microbe has now established itself throughout the Bay Area and has spread along the coast from Monterey to Humboldt County, according to a study of 16,227 trees in 16 counties in Northern California.
Millions of coast live oak and tan oak trees have withered and died over the past quarter century, leaving acres of kindling for wildfires, but the outbreak this year was one of the worst. Oak trees have historically been abundant in California and southwestern Oregon, with hundreds of millions of them stretching all the way to Baja California.
The rate of trees infected almost doubled in 2019 — from 3.5% to 5.9% — and was 10 times higher in some places compared with the 2018 survey, said Matteo Garbelotto, the director of the UC Berkeley Forest Pathology and Mycology Laboratory, which tested leaf samples taken by 422 volunteers.
Infections were found in all the well-known hotbeds, like Marin and Sonoma counties, the East Bay, Big Sur and the Santa Cruz mountains. But the 12th annual survey detected more of the pathogen this year in virtually every location. That’s mainly because the disease spreads faster in the kind of wet weather that hit California last winter, Garbelotto said.
“There was a significant increase in infection rates over last year, but that’s not totally surprising because we had a lot more rainfall,” Garbelotto said. “But it was a surprise to see them all at once. It’s telling us we are entering a different phase of the disease, where the organism isn’t really establishing itself in new areas, but is showing itself more when weather conditions are favorable.”
Sudden oak death is an exotic disease that was discovered in Mill Valley in 1995. It now exists in forests and wildlands in 14 California counties and in Curry County, Ore., just across the state border.
It kills oak trees, including California’s signature tree — the live oak — and there are 107 susceptible host plants, including such common garden ornamentals as camellias and rhododendrons. Although some hosts are sickened, they do not always die from the fungus-like ailment. Instead, these plants, bushes and trees help spread the deadly spores.
By Michelle Ma
About 450 nonnative, plant-eating insect species live in North American forests. Most of these critters are harmless, but a handful wreak havoc on their new environment, attacking trees and each year causing more than $70 billion in damage.
The problem is, scientists often don’t know which insect will emerge as the next harmful invader.
A team led by the University of Washington, drawing largely on the evolutionary history of insect-plant interactions, has developed a way to understand how nonnative insects might behave in their new environments. The team’s model, described in a paper appearing Oct. 17 in the journal Ecology and Evolution, could help foresters predict which insect invasions will be problematic, and help managers decide where to allocate resources to avoid widespread tree death.
“What makes the bad invaders so special? That has been the million-dollar question, for decades,” said Patrick Tobin, an associate professor in the UW School of Environmental and Forest Sciences and one of the project leaders. “This has the potential to profoundly change how we predict the impact of nonnative species and prioritize limited resources used to mitigate these impacts.”
The new model can quickly evaluate whether a newcomer insect, even before it gets here, has a high probability of killing a population of North American trees. To use the model, all that’s needed is information about the insect’s feeding method (wood, sap or leaf feeder, for example) and what trees it feeds on in its native range. The model will then determine whether any North American trees are at risk of dying from it.
Whether a nonnative insect takes hold and becomes destructive has more to do with the evolutionary history between the new (North American) host tree and the insect’s native host tree from its home region, Mech explained. Molecular tools that allow scientists to construct comprehensive phylogenies (or maps) of how tree species evolved was key to the team’s breakthrough.
For example, if a pine tree in Asia and another in North America diverged tens of millions of years ago, the North American pine likely wouldn’t have retained defenses against an insect that only lives with the pine in Asia. Alternatively, two pines on both continents that share more evolutionary history and diverged more recently might still share similar defenses.
The new model helps identify the evolutionary “perfect storm” for conifers, where the invasive insect still recognizes the new tree as a food source, but the tree hasn’t retained adequate defenses to keep the invader in check.
By Mary Frost
“Today is a great day for our urban forest.”
The insect that threatened to wipe out tens of thousands of the city’s trees has been squashed.
State, city and federal agencies announced on Thursday that the Asian longhorned beetle has finally been eradicated in Brooklyn and Queens, the last two holdouts in the city.
At a celebration in McCarren Park in Williamsburg, cupcakes decorated with pictures of the distinctive black insect were served to jubilant parkgoers and agriculture and horticulture experts.
“Today is a great day for our urban forest as we announce the eradication of the Asian longhorned beetle,” announced Liam Kavanagh, first deputy commissioner of the city’s Parks Department. “It was a bleak day for forestry in New York City when this pest was discovered. Half of the hardwood trees in New York State are susceptible.”
The successful eradication was the result of a decadeslong collaborative effort by multiple city, state and federal agencies, non-governmental organizations and private landowners, officials said.
These include the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, the state’s Department of Agriculture and Markets and Department of Environmental Conservation, and the city’s Department of Parks.
“It’s been a long, hard road,” USDA’s Samantha Simon said. “We knew that if it became established, the Asian longhorned beetle would threaten billions of dollars’ worth of timber [and] the maple syrup industry.”
The insect attacks maple, elm, willow, horse-chestnut, mulberry, birch, green ash, sycamore and London planetrees.
It’s been 23 years since the invasive beetle (technically not a bug) was first detected in Brooklyn. Experts believe it entered the country on wooden pallets shipped to Greenpoint.
The USDA calculated the speckled insect, about the size of a waterbug with antennae as long as its body, has wiped out more than 24,000 New York trees, and 180,000 nationwide. Thursday’s announcement marks the end of a six-year quarantine in northern Brooklyn and Queens.
To eliminate the beetle, APHIS regulated the movement of trees, firewood and woody debris and carried out surveys to find and remove infested trees. In total, APHIS removed 5,208 infested trees and treated 67,609 at-risk trees.
By Lee Shearer
ATHENS, Ga. — Climate change gets the most attention nowadays when it comes to human-caused environmental destruction, but it’s only one of the ways humans are shredding ecological webs of life.
One that’s under-reported is the growing spread of foreign plants like privet, a nondescript Asian shrub a U.S. Forest Service scientist once compared to an atomic bomb in its ability to obliterate everything around it.
Used for more than a century as a landscaping plant — the Sanford Stadium hedge is one — seven species of privet have now made their way into more than 600,000 acres of Georgia forest and countless urban and rural yards.
Other plants, mainly from China and other Asian countries, have also reached millions of acres in Georgia in a kind of slow-motion life-and-death struggle playing out in various scenarios not just in Georgia but across the world.
They get here and spread in various ways. Many brought here for planting because they’re pretty. Privet and dozens of other invasive exotic plants are a big and under-rated factor in why scientists are seeing steep declines in insect numbers and bird numbers in Georgia and elsewhere, says Georgia Department of Natural Resources botanist and ecologist Mincy Moffett.
“Invasive exotics is about extinction,” he said.
“We’re losing the Southern forest,” said Athens-Clarke County Ecological Resource Manager Mike Wharton.
When Wharton says forest, he’s not just talking about trees, but all the life in a forest — the birds that nest in the trees, the rabbits and voles beneath, the bugs or greenery they eat, even the soil micorganisms and worms.
As privet grows up in thickets, nothing can grow beneath it, and even the soil acidity is changed.
Forest researchers have found that the changed soil is more hospitable for invasive species of worms whose appetites accelerate litter composition and make soil harder, increasing stormwater runoff, Wharton explained.
Humans have been moving plants and animals around thousands of years, but the pressure on natural systems today from invading plants — privet, Japanese honeysuckle, English ivy and many more — is unprecedented, said Karan Rawlins, invasive species coordinator at the University of Georgia’s Center for Invasive Species and Ecosystem Health.
“People have always mixed things up, but in modern times it has sped up, more than a natural system can adapt to,” she said.
No one expects to be able to roll back the invasion, but state land managers, among others, are working to protect and restore what they can. Many landscapes still remain relatively untouched by non-native invasion.
Locally, the State Botanical Garden has been rolling back the exotic plants infesting its forests, and a volunteer group called the Weed Warriors saw native plants return to Athens’ Memorial Park as they worked over years to eradicate the park’s heavy load of privet, ivy and other exotics.
As Athens-Clarke’s Wharton spoke this summer, he watched a small army of volunteers from Athens’ Pilgrims Pride poultry processing plant toil for days in July heat removing privet and other invasive plants from a stretch of the North Oconee River near downtown Athens, giving a head start of years on what Wharton hopes will be a much larger restoration along the river.
When native plants return to the area, re-emerging or seeded with a recipe created by State Botanical Garden of Georgia conservationist Linda Chafin, the stretch will be a seed bank for native plantings elsewhere as Athens-Clarke land managers reclaim more exotic-occupied territory, Wharton said.
“As we pull it back, we’re going to see how beautiful this area is,” Wharton said.
Forest ecologists like Rawlins also hope state lawmakers can be convinced of how serious a threat invasive exotic plants really are.
Georgia is one of just four states that don’t have a noxious weed law that could reduce the sale and use of foreign plants known to be invasion threats.
An international conservation group is warning that more than half of the European tree species that exist nowhere else in the world are threatened with extinction.
The International Union for the Conservation of Nature said in a new report Friday that 58% of the continent’s 454 native trees are threatened and 15% are “critically endangered” – one step away from extinction.
More than 150 experts contributed to the report, which the conservancy called the first comprehensive assessment of the extinction risk of trees in Europe.
The findings in the “European Red List of Trees” come amid heightened concern about environmental issues and extinction risks in Europe and beyond. A U.N. report on biodiversity released in May warned that extinction looms for over 1 million species of plants and animals.
IUCN, a 71-year-old organization known for its “Red List” classification of threatened species, said that “invasive and problematic” species are the top threat to European trees, with urban development and “unsustainable logging” as other factors.
The group’s Europe director, Luc Bas, said “human-led activities” were resulting in population declines of important tree species.
Among the recommendations , the report’s authors called for the creation of protected areas, improved monitoring and increased research on the impacts of climate change on forests and individual tree species.
By Sam Lounsberry, Boulder Daily Camera
Even as Boulder County foresters press on in their fight against the invasive emerald ash borer harming the local tree population, officials acknowledge it is a losing battle.
But it is one lovers of ash trees don’t have to walk away from empty-handed, even as sickened trees are in line for removal or have already been sawed to stave off the infestation.
Woodworkers like Evan Kinsley, who started the Boulder-based business Sustainable Arbor Works several years ago, have turned to ash trees to supply their furniture and art crafting practices as a way to maintain the local benefit provided by the species slated for a countywide death at the hands of the insect. Emerald ash borer has already dramatically altered the composition of forests across the middle and eastern regions of the country.
“It’s a privilege to be able to work with a local hardwood like ash,” Kinsely said.
When he first learned of the 2013 detection of emerald ash borer in Boulder — it has since spread to Longmont, Lafayette, Lyons and Superior, but until last month, when it was first detected in Broomfield, Boulder County remained the only area in the Mountain West with a confirmed presence — Kinsley and his now-business partner Aaron Taddiken looked at each other and said, “We have to do something.”
The solution was to build a wood kiln to speed up the drying process for felled trees, and now Kinsely focuses on harvesting trees removed from the urban landscape, a large proportion of which are ash due to the pesky beetle’s invasion, and reusing them for wholesale lumber slabs and designing and building custom furniture.
“It used to be most of this time, that a lot of woodworkers got their wood from big wood suppliers. That would come from all over the country, all over the world,” Kinsley said. “It’s not a new thing to use local lumber. But it was a new idea for smaller woodworkers, smaller lumber mills to start working with tree (removal) companies.”
Supporting Kinsley’s living is not the life cycle he prefers for the trees, but he feels he is making the best out of a bad situation…
While the city and Boulder County continue treating public ash trees to keep them alive as long as possible using pesticide applications, tree adoption programs and biological weapons, enforcement against declining ash trees on private property continues to ramp up.
In 2018, Read said the city sent 182 letters to private property owners asking them to address declining ash trees posing safety hazard; in 2017 the number was 118, in 2016 it was 82. This year he expects to send a significantly larger number of such letters. The growing number of letters aligns with the advance of the beetle infestation. Tree owners who receive such a letter will have to show the city a good-faith effort is being made to remove trees considered dangerous.
But work to preserve ash trees still free of the emerald ash borer goes on, even as replanting species that won’t be affected by the invasive bug remains the focus of foresters for the future of Boulder’s canopy. The city’s Tree-Imagine campaign launched this spring is pushing city residents to collectively plant 25,000 new trees by 2025.
The county this summer introduced a swarm of a non-stinging, parasitic member of the wasp family on the Mayhoffer open space property in Superior, and also has enlisted 159 participants in its adopt-a-tree program for ashes slated for removal from public places. Program participants can choose to commit to pay for treatment to keep the trees alive.
“A lot of these ash trees are old and they’ve been with the community a long time,” Kinsley said. “Trying to protect them in every way is a valiant effort.”
By Chrissy Sexton
Professor Matthew Evans from the University of Hong Kong created a computer model to estimate how ash dieback disease may affect the UK’s 125 million ash trees.
Human-induced changes to the environment are increasing the rate at which pests and diseases are introduced, which is severely threatening to native species. Long-lived species that reproduce slowly, such as forest trees, are particularly susceptible to new pathogens.
It is estimated that in 2015, 100 million hectares of forest were affected by pests and diseases around the globe. However, the subsequent impacts to any given forest ecosystem cannot be detected for years, so experts use computer models to predict future outcomes.
In a recent study, Professor Matthew Evans from the University of Hong Kong created a computer model to estimate how ash dieback (ADB) disease may affect the UK’s 125 million ash trees.
ADB disease, which is caused by a fungus native to East Asia, was introduced to the UK seven years ago. This incurable infection leaves diamond-shaped scars on the bark and causes the leaves to fall off of the trees.
About one in every 100 ash trees is able to resist the fungus and avoid infection. This is likely due to a genetic advantage which allows the trees to shed their leaves earlier to prevent the fungus from establishing itself.
Professor Evans found that at the current level of resistance, 95 percent of the UK’s ash trees could be wiped out by the end of the century. He determined that breeding more ash trees with resistance will prevent millions of deaths.
By Bruce Scruton
MIDDLE SMITHFIELD, Pa. — Three species of a small wasp that can attack the eggs of the emerald ash borer were released by National Park Service biologists within the Delaware Water Gap National Recreation Area this past weekend.
The borer, an invasive beetle from Asia, is capable of killing a full-grown ash tree within a couple of years and has been found in several locations in Sussex County in the past two years.
The release was in the Mosier’s Knob area, just below the Walpack Bend of the Delaware River and across the river from Worthington State Forest where the New Jersey Department of Agriculture recently released its own biological agents to stem the invasion of the pest.
Kara Deutsch, chief of resource management for the park, said the emerald ash borer has been found on both sides of the river. The choice of Mosier’s Knob for the release came at the recommendation of regional NPS experts.
The wasps, known in scientific circles as “parasitoids,” were supplied by the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) and came from the Plant Protection and Quarantine (PPQ) EAB Parasitoid Rearing Facility in Brighton, Mich.
There were three species of wasps released — one release was of adults and the others were pupae of separate species.
The three are themselves invasives, native to the Asian areas where the emerald ash borer are native. The borer was imported to this area first identified in the area around Detroit and believed to have arrived in 2002 inside of wooden packing material.
In less than two decades since, the borer, a type of beetle, has been found in the U.S. from the Atlantic Coast (except Forida) as far west as Colorado and has spread throughout the eastern two-thirds of Canada.
The wasp parasites — the adults are about the size of a mosquito and don’t sting — get the borer in both egg and larval states.
The adult Oobius agrili female will lay her own egg inside the egg of an ash borer and there are two life cycles of the wasp for one life cycle of the borer. In experiments and observation, more than half an emerald ash borer’s eggs became victims of the wasp.
The other two wasps attack the larval stage of the borer and it is that stage that causes the damage to ash trees.