Tree-killing pests: Who? Where? How?

by Loose Leaf Contributor

By Faith Campbell, Emeritus environmental advocate and tree-pest expert

Nearly 500 non-native insects and disease-causing pathogens have been introduced to the United States in the 400 years since European settlement began. Here are some examples:

A map showing an area of the Northeast affected by hemlock woolly adelgid.

A map showing an area of the Northeast affected by hemlock woolly adelgid. Click to zoom in.

  • Chestnut blight has virtually eliminated mature American chestnuts across the species’ range, which is most of the eastern deciduous forest.
  • European gypsy moth periodically causes severe defoliation of several hardwood species, especially oaks. The gypsy moth now occupies forests from New England to a line reaching from Virginia to Wisconsin.
  • Hemlock woolly adelgid has killed 90 percent of hemlocks in groves spanning from Maine to Georgia. These hemlock groves form unique ecosystems that shelter specific bird, fish, salamander, and plant species.
  • Emerald ash borer (EAB) has spread over 25 years to more than 100,000 square miles across 23 states and two Canadian provinces. EAB is likely to kill most trees belonging to two dozen species of ash in the U.S., Canada and Mexico.
  • White pine blister rust has reduced populations of several western white pines. The greatest threat is to high-elevation pines — whitebark, limber and bristlecone — which are the base of food webs and protect snow cover that is the foundation for water supplies in the West.
  • Sudden oak death has killed more than 1 million tanoak and oak trees in the coastal mountains of California and southern Oregon. Many tree and shrub species vulnerable to this disease grow in eastern forests, so scientists worry that the pathogen might become established there.

The U.S. Forest Service offers a database of tree pests and diseases that have been documented across the country. [Simply select your state and/or county from the drop-down menus to see which pests are damaging trees in your region or city.]

The Northeast and Pacific coasts contain the most number of tree pests and pathogens.

The Northeast and Pacific coasts contain the most number of tree pests and pathogens.

Northeastern states have traded with Europe and Asia for about 400 years, which explains why the region has the most established non-native tree-killing pests: 62 in New York; 58 in Pennsylvania; 57 in Connecticut; 55 in New Jersey. Pacific coast states have been trading for only about 150 years, but they are catching up: There are now 42 pests in California; 41 in Washington and 36 in Oregon. In California alone, non-native forest pests now make up one-third of the damaging pests in the state — up from only 10 percent just 50 years ago.

How did these insects and disease-causing pathogens invade the U.S.? Most arrived on imports of plants or in the crates, pallets, and other types of packaging made from wood. In my follow-up posts, I’ll go into more detail about these pest-ridden pathways and what governments, importers and private citizens can do to help prevent additional introductions and spread of established pests to other vulnerable areas.

Forest Digest — Week of September 8

by American Forests

Another week and another Forest Digest. See what’s happening in the world of trees:

  • “Climate change accelerating death of Western forests”USA Today
    A study by the Union of Concerned Scientists and the Rocky Mountain Climate Organization shows that drought, insect pests and wildfire — forest threats exacerbated by climate change — are killing off millions of acres of the Rocky Mountain range’s pine and aspen forests.
American Forests is working to protect high-elevation forests in the Rocky Mountain range through our Endangered Western Forests initiative.

American Forests is working to protect high-elevation forests in the Rocky Mountain range through our Endangered Western Forests initiative.

  • “Consumer Goods and Deforestation”Forest Trends
    A recent study by Forest Trends found that 49 percent of all recent tropical deforestation is the result of illegal clearing for commercial agriculture.

Whitebark pine: Strategy in the Greater Yellowstone Area

by Christopher Horn

Whitebark pine ecosystems face pest, disease and climatic threats that have — and could further — wreak havoc on stands of this keystone species. Fortunately for the trees, and the plants and wildlife that rely on them to survive, American Forests and our partners in the Greater Yellowstone Area are working towards solutions that can save the species.

One of those partners is Nancy Bockino, who is leading an effort with the Greater Yellowstone Coordinating Committee Whitebark Pine Subcommittee to update the GYCC’s Whitebark Pine Strategy, an all-encompassing outline of priority projects, including defining new management tools and revising high-priority restoration sites.

Forest Digest — Week of September 1

by American Forests

Another week and another Forest Digest. See what’s happening in the world of trees:

  • “Fires and drought have transformed New Mexico forests”Las Cruces Sun-News
    New Mexico is also dealing with forestry setbacks because of drought, as well as extensive wildfire damage. Up to 18 percent of the Southwest’s forests were lost to wildfire and bark beetle outbreaks — both issues related to a warming climate — between 1984 and 2006.
  • “Native forests need proper preservation from urban sprawl”The Miami Hurricane
    Dozens of acres of pine forest on the campus of the University of Miami in Florida could potentially be lost to urban sprawl. Students and members of the surrounding community are working to ensure the preservation of these trees.

Water supply and the whitebark pine

by Christopher Horn

American Forests helped leverage National Park Service (NPS) funding in the Greater Yellowstone Area (GYA) to estimate the Available Water Supply (AWS) for the 176 long-term whitebark pine monitoring sites. NPS personnel had previously started gathering data in 2013, but limited funding paused the project.

Many people — including project lead David Thoma, an hydrologist with the National Park Service — were enlisted by American Forests to coordinate the new AWS estimate project. The team also included Dr. Henry Shovic has proven local experience and expertise in soils, soil interpretations, soil survey, scientific analysis and documentation, remote sensing, and geo-spatial analysis. He has recently completed preliminary work on AWHC and AWS for Yellowstone National Park and the GYA, and has already compiled large amounts of necessary soils data, as well as having completed this work for 60 whitebark pine long-term monitoring sites.

We asked Thoma some questions about the project:

Q: What were some of the major goals for soil testing in the Greater Yellowstone Ecosystem?
A: We use information about soil properties to help understand how much water is available to trees and for how long. This property of soil, called water holding capacity, is especially important in dry years. The goal of this project was to obtain estimates of water holding capacity at the stand level in remote areas. This in turn helps us understand how trees respond to forest disease agents like mountain pine beetle, which are more lethal to trees when trees are drought stressed.

Q: Were there any startling or hopeful discoveries?
A: Our preliminary results suggest that the water supply for trees, which is affected by soil properties, is important for determining the probability of tree mortality if the tree was attacked by mountain pine beetle.

Q: How do you see this information being used? How is it most beneficial?
A: This information can be used by managers to select planting sites in the Greater Yellowstone Area according to soil properties that will increase the probability of tree survival, even when trees are attacked by mountain pine beetle.

Thoma, D., K. Irvine, H. Shovic, E. Shanahan, K. Legg 2014. Climatic controls on mountain pine beetle mediated mortality in whitebark pine in the GYE. Oral presentation at the Yellowstone Biennial Science Conference, Oct 6-8 Mammoth, WY.

How large does the blue spruce grow?

by Loose Leaf Contributor

By Robert T. Leverett, Native Tree Society

Blue spruce

The 324-point blue spruce spotted by Will Blozan. Credit: Will Blozan

How tall do blue spruces grow? Ornamental yard trees often reach 60 to 80 feet and 1.5 to three feet in diameter. Ostensibly reliable internet sources vary greatly on listed maximum heights. Some say more than 100 feet. Others cap the species off at 80, while one source lists 50 meters, or 164 feet. There’s little agreement, but the species pays no attention to such nonsense. Blue spruces know what they’re genetically programmed to do, and in southwestern Colorado, the blues achieve their best growth. The Western Native Tree Society (WNTS), supporting the American Forests National Big Tree program, discovered a blue to break all records in the La Plata Mountains this August.

Near Hermosa Creek, the team of Will Blozan, Matt Markworth, Larry Tucei, Chris Morris and Mark Rowe measured a huge blue at 165.5 feet tall, 12.5 feet in girth and 32.5 feet average crown spread. It was eagle-eye Will’s discovery and totals 324 points via the American Forests champion tree formula. The current national champion in Utah totals 331 points, making the Colorado tree a contender for co-champion under the large-tree rule — that a tree that measures within five percent of the champion’s points is eligible to become co-champion. The intrepid team also measured another blue at 164 feet tall and 10.1 feet around. But that was hardly the end of the discoveries.

blue spruce

The team at the base of the 324-point blue spruce. Credit: Will Blozan

Later, going solo, Matt confirmed a 155-foot blue with a 12.9-foot girth and 33.5-foot crown spread, earning the specimen 319 points and making it eligible for co-champion. Then it happened: Matt measured a pencil-straight giant at an astounding 178.8 feet, the tallest we know of — anywhere. The tree measures 10.9 feet in circumference. Its narrow crown averages only 23.5 feet for a total of 309 points. It may not be eligible for co-champion this year, but it’s height has blown records out of the water. It seems to be part of a trend; Matt measured other blues between 162 and 158 feet high. The number of blues measuring more than 150 feet is growing.

Champion trees show us the full potential of their species and these Colorado blue spruces are a prime example of that. In October, the world will find out whether any of the trees had their co-champion status confirmed and made it onto the National Register of Big Trees. But, whether they end up wearing that crown, they have shown us not to underestimate the blue spruce.

An engineer by education, Robert T. Leverett is the co-founder and executive director of the Native Tree Society. He writes from Florence, Mass.

Note that these trees were all measured with LTI TruPulses (200s and 360s) using the sine method, accurate to +/- 0.5 feet. (See the American Forests webinar on measuring tree height.)

Introducing tree-pest expert Faith Campbell

by Christopher Horn

Homepage photo credit: Kyle Ramirez

Faith Campbell knows a thing or two about trees and the insects that threaten them. She brings years of experience, including her most recent post at The Nature Conservancy, to Loose Leaf as one of our new guest bloggers.

Before diving into the interesting and sometimes volatile relationship between trees, insects and humans, we wanted to learn more about Faith herself:

What led you to the forestry field, and tree pests in particular?
I have always loved trees and natural areas. In the 1950s, when I was growing up in northern Virginia, the streets and parks of Washington, D.C., still looked like cathedrals because of the interlocking branches of elm trees. I learned about Dutch elm disease, and then that additional non-native pests were killing chestnuts, hemlocks. I wanted to do something to reduce this threat.

Faith Campbell, Loose Leaf's new guest blogger, has years of expertise in trees and insect pests.

Faith Campbell, Loose Leaf’s new guest blogger, has years of expertise in trees and insect pests. Photo credit: Faith Campbell.

What are some tree-versus-pests successes you’ve observed in your career?
The biggest success has been with the Asian longhorned beetle (ALB) — although that story is not yet over. Determined efforts by federal, state and local agencies, private citizens working individually, and organizations and funding associations, have succeeded in eradicating several outbreaks and they are making progress on other outbreaks. Also, the detection of several ALB outbreaks persuaded U.S. and Canadian policymakers that wood packaging (crates, pallets, etc.) is a high-risk pathway, so they led global efforts to require treatment of wood packaging. As I said earlier, this story has not reached its end — additional outbreaks of ALB continue to be found, and the treatments required for wood packaging have not yet eliminated the risk from that pathway. More remains to be done. But this situation points the way we should go and the level of effort needed.

Have there been any infestations that have threatened a particular tree species to the brink of endangerment or extinction? If not, are there any suggestions that this could happen in our lifetimes?
While none has yet driven a species quite to the brink of biological extinction, many of the non-native pests have caused the host species to decline to the point that it can no longer perform its role in the ecosystem. American chestnut has been reduced almost everywhere to short-lived root sprouts that cannot provide the huge crops of nuts that formerly sustained wildlife ranging from black bears to squirrels. Port-Orford cedar, several of the western white pines, and eastern hemlocks have been severely reduced over large portions of their ranges. The greatest threats currently are to the high-elevation, five-needle pines of the mountain west and to redbay in coastal regions of the southeast. The U.S. Forest Service Forest Health Technology Enterprise Team projects that redbay will lose 90 percent of its basal area throughout its range by 2027 — just 25 years after the insect-fungus combination was detected.

Is there a pest in particular whose effects on forests worry you?
Dozens! I will name two that pose severe threats, but to which state and federal plant health agencies have failed to respond: the goldspotted oak borer (GSOB) and polyphagous shot hole borer (PSHB). The GSOB has killed more than 80,000 trees in San Diego and Riverside counties in California over perhaps just 20 years. It threatens coast live oak, black oak and canyon live oak throughout the state, and north into southern Oregon. The PSHB is already established across most of the Los Angeles basin, with a separate outbreak in San Diego County. PSHB is known to attack close to 300 different tree species, including nearly all the trees that grow in riparian areas in southern California. The fungus that it transports is known to live in more than 100 species. Trees considered reproductive hosts for the beetle include five types of maple trees, five oak species, two sycamore or plane trees, and several species common in the nursery trade such as camellia. Some of the hosts, such as box elder, are widespread in the eastern U.S. as well as in California. Yet the California Department of Food and Agriculture and USDA Animal and Plant Health Inspection Service have not developed programs aimed at preventing the spread of these insects.

Where do you see the relationship between trees and invasive insects in the next decade? What can we — NGOs, government agencies, corporations and U.S. citizens — do to help ensure the healthy and vitality of our country’s forests?
Over the next decade, non-native insects and pathogens will continue to enter the United States; and the nearly 500 species already here will continue to spread. Additional tree species will face threats from new invaders, and trees formerly protected by distance from pest outbreaks will be put at risk by the established organisms’ spread. To reduce the devastation to the greatest extent practicable, government agencies, corporations, citizens and organizations can adopt practices that minimize the presence of pests in items that they move from one place to another. High-risk articles include wood in many forms: firewood, logs or burls used in woodworking, decorative items or rustic furniture; crates, pallets, spools for cable; as well as plants for our gardens. In future blog posts, I will discuss the specifics of what government agencies, corporations and citizens can do.

Read all of the posts in Faith’s tree-pest series:

  • Tree-killing pests: Who? Where? How? — Nearly 500 non-native insects and disease-causing pathogens have been introduced to the United States in the 400 years since European settlement began. Learn more about some of the most notorious perps.
  • Shipping containers: Importing insect pests, too — Each day, 35 shipping containers bring an invasive pest to the U.S., threatening the country’s native tree species and wreaking havoc on our urban and wildland forests.

Forest Digest — Week of August 25

by American Forests

Summer is winding down, but our Forest Digest is still going strong.

Check out this week’s news in trees:

American Forests reforested a former mining site in southeast Ohio, marking the first project of its kind in our Global ReLeaf program.

American Forests reforested former mining site in southeast Ohio, marking the first project of its kind in our Global ReLeaf program.

  • “Judge blocks Montana from logging in grizzly territory”Reuters
    A federal judge ruled last week that a permit that opened up Montana’s Stillwater State Forest to timber harvests violated the Endangered Species Act. The area in question constituted nearl 37,000 acres that serve as habitat for protected grizzly bears.
  • “Program focuses on loss of young forests”Chillicothe Gazette
    Young forests in Ohio are in decline, which is impacting some of the state’s wildlife populations. The Ohio State University Extension is leading the program, which aims to raise awareness among woodland owners and forest enthusiasts.

Forest Digest — Week of August 18

by American Forests

It’s Friday and Forest Digest is back!

Check out this week’s news in trees:

American Forests planted moringa trees in a 2011 Global ReLeaf project in Ghana.

In 2011, American Forests planted moringa trees in a Global ReLeaf project in Ghana.

  • “New analysis links tree height to climate”University of Wisconsin-Madison
    A botany professor at the University of Wisconsin-Madison studied how tree height, resource allocation and physiology vary with climate in Australia’s Victoria state.
  • “Some trees face ‘extinction’ threat”CBS Moneywatch
    Pests and diseases are infiltrating forests around the globe. One of them — the emerald ash borer — could cause the extinction of North American ash trees, says one researcher.

A presidential plea

by Christopher Horn

Last week, American Forests launched its first-ever petition through TakePart’s Take Action forum — a letter to President Obama to make forests play an important role in the country’s climate change plan — and have seen a tremendous amount of people from across the world sign on.

Forests across the country and world are succumbing to a range of threats, from drought and wildfire to pests and diseases, all of which are exacerbated by climate change.

Forests across the country and world are succumbing to a range of threats, from drought and wildfire to pests and diseases, all of which are exacerbated by climate change.

President Obama announced the initiative in July, highlighting rising temperatures, carbon pollution, and the country’s preparedness for the impacts of climate change.

Forests and climate change have a dynamic relationship. Trees absorb carbon dioxide, one of the biggest contributors to climate change, and convert it into clean oxygen, which they release, and carbon, which they store. Sound forest management practices and increased funding can help these important natural resources maintain and improve their potential to sequester carbon, maximizing their ability to mitigate climate change.

Please take a moment to sign the petition and share with your friends and family on Facebook and Twitter. With your support, we can encourage the president and his staff to ensure that forests have a place in our country’s — and world’s — climate change conversation.