Friday, March 20, 2015

Forest Pest Surveying: The Next Generation

Tom and Lenny use binoculars to scan tree bark for invasive insect exit holes.  Emerald ash borer exit holes are shaped like a D while Asian longhorned beetle exit holes are round and the size of a dime.  Forests, the final frontier. These are the voyages of forest pest surveyors. They’re lifelong mission: to explore strange new woodlands, to seek out invasive insects and pests that harm trees, to boldly go where no pest surveyor has gone before.

Invasive insects are to conservationists like Romulans are to Vulcans. Emerald ash borer, Asian longhorned beetle, hemlock woolly adelgid, and balsam woolly adelgid threaten the economy with costly tree removal, environment with adverse impacts to forest health, and public safety with dead limbs that fall on cars and homes. They found their way from their Eurasian home range to the United States in nursery stock and wood packing materials. Without the natural checks and balances found on their home turf, they reproduce as fast as tribbles. Forest pest surveys are important because early detection leads to rapid response and better management options.

On a below zero morning at the end of February, I teamed up with my coworker Lenny Croote, Tom Colarusso of the Animal and Plant Health Inspection Service, and volunteer Spencer Eich for an invasive insect forest survey at Limekiln Lake campground in Inlet. This campground is large and receives a lot of traffic, making it an ideal place for a survey because invasive insects hitchhike in untreated firewood.

Spencer and Tom spot heavy woodpecker damage in a tree, possibly indicating an invasive insect infestation.  Spencer recently graduated from the State University of New York College of Environmental Science and Forestry with a strong interest in invasive species and this was his first forest survey. Tom explained to him that trees are scanned with binoculars for signs and symptoms of invasive insects. Winter is a great season to check trees because a clear view of the canopy branches is available without interference from leaves.

We snowshoed to the main gate and pulled out our binoculars. Tom said that ash may not be common in this campground. The shoreline of Limekiln Lake makes for wet conditions, and these areas are usually dominated by maples and pines. The drier soils of the upland slopes are characterized by northern hardwoods like birch, beech, and maple.

Woodpecker damage is one infestation sign that we were on the lookout for. Woodpeckers find emerald ash borer to be particularly tasty. Foraging holes or blonding (bark removal) on ash trees are red flags for further investigation.

Our team also checked trees for exit holes. Adult emerald ash borer and Asian longhorned beetles chew exit holes in the bark once they have completed their life cycle from the egg, larvae, and pupae stages in the tree. Emerald ash borer exit holes are shaped like a D and are found in all ash species including white, green, black, and blue. Asian longhorned beetle exit holes are round, the size of a dime, and found in hardwood trees including maple, horsechestnut, willow, elm, ash, and birch, among others. Tom noted that Asian longhorned beetles often infest the top of a tree first, then work their way down.

Woodpecker damage like these holes created by a sapsucker is an initial clue to an invasive insect infestation.  Tree damage occurs when emerald ash borer and Asian longhorned beetle larvae tunnel under the bark and disrupt tissue that transports water and food. With large infestations, trees starve to death in just a few years.

We also zeroed in on signs of hemlock and balsam woolly adelgid. The hemlock woolly adelgid produces a waxy, white “wool” to shield against predators and dry conditions. These insects feed on sap and nutrients at the base of needles. Feeding damage interferes with nutrient transport, turns green needles gray-green and causes them to fall off. Defoliation prevents photosynthesis, impacts tree health, and may cause death.

Emerald ash borers leave D-shaped exit holes in tree bark.  Photo credit:  Daniel Herms, The Ohio State University, Bugwood.org.  Balsam woolly adelgid feeding damage causes twig gouting, resulting in swollen branches that cause the tree to choke itself to death. Trees survive a long time with twig gouting. Stem infestations, on the other hand, can kill a fir tree in 3 to 10 years. We checked trees for white wooly dots on the bark; yellow, brown, or red needles; and split or curled crowns.

Besides the ubiquitous beech bark disease, no forests pests were detected during our survey of Limekiln Lake campground. The beech scale insect attacks bark, making beech trees susceptible to fungal invasion. Tom, Lenny and I have been conducting forest surveys as a team since 2008 and have spotted beach bark disease every year.

A hemlock woolly adelgid infestation.  Photo credit:  USDA Forest Service - Region 8 - Southern Archive, USDA Forest Service, Bugwood.org.  Spencer, the next generation of conservationists, took part in a day of learning in the field and fun. Having a career in the eradication and management of invasive species is one of Spencer’s goals because he is passionate about preserving the Earth’s natural ecosystems, and recognizes the environmental, agricultural, and economic damages that are posed by invasive species. During this shadowing field experience, he learned how to detect the presence of invasive pests by observing the damages they cause to trees. Tom gave Spencer specific details about what species of trees are susceptible to pests, the particular section of tree to observe with scrutiny for signs of invasion, and coloration differences on the exterior of the tree that may indicate insect exit holes. Spencer had never been on snowshoes before, and snowshoed like a pro by the end of the survey.

This particular survey will stick in my memory not because of the brutal cold or the great relief I felt when no invaders were found, but because I watched Spencer learn new technique. He brimmed with questions, an eagerness to learn, and a desire to help stop the invaders.

A balsam woolly adelgid infestation.  Photo credit:  Ladd Livingston, Idaho Department of Lands, Bugwood.org.  In addition to offering Spencer a shadowing experience, my personal understanding of forest pests was enhanced. Tom always shares with me tips that improve my tree identification skills. He also talks about cutting edge research that keeps me up to speed with new developments. For me, it doesn’t get any better.

If you want to learn more about forest pest surveying, Scotty can beam you up to the Invasive Insect Enterprise for a showing of the Invasive Insect Forest Surveying video.   To learn more about invasive insects visit the APHIS Hungry Pests website.

Invasive insect forest surveys will allow us all to live long and prosper.

Photos, from above: Tom and Lenny use binoculars to scan tree bark for invasive insect exit holes. Emerald ash borer exit holes are shaped like a D while Asian longhorned beetle exit holes are round and the size of a dime; Spencer and Tom spot heavy woodpecker damage in a tree, possibly indicating an invasive insect infestation; (left) Woodpecker damage like these holes created by a sapsucker is an initial clue to an invasive insect infestation; (right) Emerald ash borers leave D-shaped exit holes in tree bark (photo courtesy Daniel Herms, The Ohio State University); This exit hole was made by the Asian longhorned beetle (photo courtesy Daniel Herms, The Ohio State University); A hemlock woolly adelgid infestation (photo courtesy USDA Forest Service – Region 8 – Southern Archive, USDA Forest Service); and a balsam woolly adelgid infestation (photo courtesy Ladd Livingston, Idaho Department of Lands).


Caitlin Stewart is Conservation Educator at the Hamilton County Soil and Water Conservation District (HCSWCD). One of HCSWCD’s largest programs is their Invasive Species program and Caitlin will be sharing her field experiences, as well as the efforts and results of forest surveys, and monitoring and management.

Caitlin has deep roots in Hamilton County as both her grandparents purchased property on Sacandaga Lake and Lake Pleasant in the 1960s. Her parents met and were married in Lake Pleasant, and she spent summers and vacations there. She’s been a full time resident since 2008 and is an avid hiker, skier, paddler, runner and biker.




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