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Plant Protection Today - Eradicating a Tree Killer

Eradicating a Tree Killer
August 19, 2019
(Cover Photo Source: Melody Keena, USDA Forest Service,

PPQ Closes in on the Asian Longhorned Beetle

By Greg Rosenthal

The Asian longhorned beetle is a destructive tree pest from Asia.For more than 20 years, USDA’s Plant Protection and Quarantine (PPQ) program has fought to save America’s trees from a certain killer—the Asian longhorned beetle. Today, the battle continues, but the beetle is quickly losing ground.

A Strange-Looking Beetle Arrives in America

In August 1996, a Brooklyn, New York, resident noticed a showy, jet-black beetle. It sported white spots on its back and waved long antennas with alternating black and white bands. That discovery marked the first U.S. detection of the Asian longhorned beetle (ALB), a wood-boring invasive pest that normally lives in China and on the Korean peninsula. As ALB larvae chew deep into a tree’s heartwood, they disrupt the tree’s flow of water and nutrients, from its roots to its leafy canopy. When this disruption becomes severe, it kills the infested tree.

PPQ and New York State Department of Agriculture and Markets officials responded immediately. They knew that if this invasive insect became established in the United States, it would threaten forest resources valued at billions of dollars, along with the many industries those forests support—like timber, recreation, and maple syrup production.

“ALB likely arrived hidden in untreated wood packaging material like pallets and crates from China or Korea, before we had international standards for treating this material to prevent the spread of insects,” said ALB National Policy Manager Paul Chaloux. “The beetle feeds on numerous hardwood species, especially maple, but also ash, birch, elm, poplar, and willow, among others.”

Today, PPQ and our State partners are successfully battling ALB populations in Massachusetts, New York, and Ohio. We have already eradicated it from Illinois, New Jersey, portions of New York (Manhattan, Staten Island, and Islip), portions of Ohio (Stonelick and Monroe townships), and Boston, Massachusetts. PPQ expects to declare eradication this fall in all areas of New York City. Despite these successes, we have many years ahead of us before we can declare eradication nationwide.

People Can Spread this Slow-Moving Pest

ALBs are happy to live generation after generation on the same tree. As a result, infestations spread slowly—unless people give ALB a ride. People can accidentally move these beetles across continents and oceans, or State, county, and city borders

Early beetle life stages—eggs, larvae, and pupae—stay hidden inside wood packaging material (WPM) like crates and pallets, firewood, logs, branches, wood debris and trimmings, stumps, and lumber. That means international cargo transporters, landscapers, and campers could easily move ALB short or long distances, accidentally starting new infestations.

Asian longhorned beetle early life stages include (left to right) egg, larva, and pupa.

A tree crew uses a wood chipper to dispose of tree debris.

PPQ Creates an Eradication Game Plan

Early identification and eradication are critical to controlling ALB’s spread. Fortunately, PPQ developed a proven eradication protocol:

  • Surveying for ALB
  • Establishing quarantine areas
  • Removing infested and high-risk trees
  • Chipping tree parts and debris to kill ALB life stages
  • Requiring compliance agreements for tree service, landscaping, and firewood companies operating in quarantine areas, so they follow our regulations to prevent ALB’s spread
  • Raising public awareness through outreach campaigns

Public engagement is vital to achieving early identification. Interestingly, a member of the public—not a professional—has discovered every new ALB infestation.

Challenges Fighting ALB

(Left) Ground inspectors use binoculars to search for Asian longhorned beetle infestations. (Right) Tree climbers scour tree branches for signs of the beetle.

“PPQ has no effective trap and lure to help detect ALB,” said Josie Ryan, National Operations Manager for ALB. “That means employees must visually check every tree in a survey area, using binoculars, bucket trucks, or our professional ALB tree climbers.”

The climbers use rope and safety gear to scale towering trees and, with the agility of acrobats, look at every square inch of every trunk and branch for signs of ALB infestation. Unfortunately, infestations usually begin in the treetops, the hardest part of the tree to see or reach.

“Declaring eradication takes several survey cycles, each taking multiple years,” Ryan explained. “Removing infested and high-risk trees is the key to eradication—and is also an expensive and difficult task.”

In Massachusetts, New York, and Ohio, more than 180,000 trees have been removed to date. Firewood is always a wildcard; ALB can move vast distances riding inside untreated firewood.

Given all of these challenges, it’s no wonder the ALB Eradication Program has cost more than a $750 million over the last 22 years. Fortunately, that investment has already delivered many successes.

Infestations Move Slowly and Leave Telltale Signs

Certain aspects of ALB’s biology and behavior help PPQ eradicate the pest. Generation after generation often complete their life cycles on the same tree, so infestations expand slowly on their own. And fortunately, infestation signs are relatively easy to spot: egg sites, exit holes, frass (sawdust and excrement that larvae create as they tunnel through a tree), and canopy dieback. 

Signs of the Asian longhorned beetle

Image of Adult beetle

Adult beetles in the summer and early fall (these big insects—1 to 1.5 inches long—have black bodies with white spots and long antennas with black and white bands).

Round holes at least three-eighths of an inch in diameter.

Pits on bark, chewed by the female beetle, where eggs are deposited.

Accumulation of sawdust-like material (insect waste) around base of tree or branches.

Dieback in the tree canopy or unseasonable change in leaf color.

PPQ Applies Science and Technology to Eradicate ALB

PPQ’s Science and Technology (S&T) supports the program by developing methods to help eradicate ALB. For example, S&T’s studies determined that host tree debris must be chipped to less than 1 inch in any dimension to kill all ALB life stages. Chipping is now a critical part of our regulatory requirements for safely moving potentially infested material out of a quarantine area. In addition, S&T has explored:

  • Using camera-equipped unmanned aircraft systems to assist with surveys and to inspect otherwise inaccessible or hazardous trees
  • Training detector dogs to sniff out ALB-infested trees
  • Developing traps and lures for monitoring high-risk areas such as port environs

Although these three methods have not yet become operational, they hold promise for improving the eradication program.

In a PPQ test, an unmanned aircraft system flies in a forest looking for mock Asian longhorned beetle damage.

WPM: A Global Problem

Untreated wood packaging material can hide various stages of wood-boring pests.ALB isn’t the only tree pest that traveled to our country as a passenger inside WPM. The emerald ash borer also likely arrived via the WPM pathway and went on to kill more than 100 million U.S. ash trees. More than 1.6 billion wood pallets circulate across the Nation daily, and billions more circulate worldwide. That makes untreated WPM a staggering global problem for spreading wood-boring pests. Fortunately, the International Plant Protection Convention (IPPC)—an international agreement with 183 countries, including ours—offers a global solution.

With PPQ as a driving force, the IPPC adopted an international standard requiring WPM to be properly treated and marked with an official stamp before it can be moved in international commerce. Regionally, the North American Plant Protection Organization (NAPPO) helps other countries build their capacity to comply with the standard, known as International Standard for Phytosanitary Management 15. NAPPO provides training, best practices, and technical information throughout the Western Hemisphere. Since its implementation, U.S. interceptions of infested wood packaging material have gone down by as much as 52 percent.

Help Save America’s Trees from ALB!

Calling all tree lovers—August is Tree Check Month, and we are urging everyone to go outside and check their trees for signs of the Asian longhorned beetle (ALB).

Now’s the perfect time to develop habits that protect trees all year. It’s not hard. Just:

  • Become familiar with the insect and its damage because early detection is critical (see “Signs of the Asian longhorned beetle” above).
  • Inspect trees regularly and report any signs or symptoms by visiting or calling 1-866-702-9938.
  • Don’t move untreated firewood—you could be moving the pest.

Remember: Even after August, you can still take these steps to protect America’s forests against the ALB!

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