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.
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.