Don't Bug Me!
Beginning with early colonists who landed in the New World loaded with dreams, grit and perhaps the continent’s first alien forest pests, and continuing today with the expansion of global trade, the northeastern United States has been ground zero for damaging non-native forest pest invasions. This month, we feature a scientist, research, a product and a partnership focused on forest pests that have found their way to our neck of the woods, and Northern Research Station scientists’ work to stop their spread.
Ever increasing volumes of both world trade and travel have opened the door for invasive insects to land on U.S. shores and possibly become established. Invasive insects can wreak havoc on ecosystems where trees lack defense mechanisms to protect themselves against damage and death, and invading insects are free of natural enemies. Melody Keena, a research entomologist with the USDA Forest Service, is on a mission to detect, monitor, contain and eliminate newly introduced invasive insects that pose threats to the United States.
Even as a child, Keena was interested in the natural world. “I think my interest in entomology started with me catching and having western fence lizards as pets. They need live insects to eat so I started finding different insects for them and got interested in how insects feed and develop,” she said.
Despite the early interest in insects, Keena began her college career at the University of California, Davis as a veterinary medicine major. After the first year though, she switched majors to entomology and ultimately earned Bachelor’s, Master’s, and PhD degrees.
Keena works at the Northern Research Station lab in Hamden, Conn., where she spends a lot of time in the quarantine lab raising invasive insects in a sealed facility in order to gather more biological information about them. This includes learning when they emerge, the length of various life stages, when they mate and lay eggs. Understanding these factors gives land managers and researchers greater ability to detect, monitor and control invasive insects.
Currently, Keena is conducting research on two invasive insect species, citrus longhorned beetle and spotted lantern fly, both having potential to become major forest pests in the United States. “In both cases some is known about the insect’s biology and behavior but not enough to effectively deal with them,” said Keena. “I will soon be collecting the data needed to develop phenology models for both species that will allow us to develop management strategies and predict the potential ranges of these insects.”
In addition to her work with insects, Keena enjoys working with numbers in many ways, not just for research, but also in keeping budgets for her research unit and church, and tracking energy use at the Hamden facility. In her limited free time, Keena enjoys photography, painting and bowling.
Comprehensive Overview of Hemlock Woolly Adelgid
The majestic hemlock, towering 60-70 feet above the forest floor, is a foundational tree in eastern forests of North America, but sustainability of the iconic tree is now threatened by the hemlock woolly adelgid (HWA), an invasive insect pest. An HWA infestation can kill a hemlock tree in the southeastern United States in just 1-3 years. A recent article published in the Journal of Integrated Pest Management provides a comprehensive overview of hemlock woolly adelgid including its biology, life stages, distribution ecology and methods of detecting and controlling the insect. This compilation serves as an important reference and tool in helping people develop forest management plans to reduce HWA impacts and, scientists hope, keep hemlocks on the landscape far into the future.
Hemlock woolly adelgid was accidently introduced to Virginia from Japan sometime before 1951, when it was first discovered in the eastern United States (it is native to northwestern North America). With few natural enemies in the introduced range, HWA has spread to 20 northeastern states and one Canadian province threatening the hemlock population. Presenting an additional challenge to controlling the pest, when infestations are small they are hard to detect and may be missed. Also, over time HWA has developed greater tolerance for cold which in earlier years was a key factor in insect mortality over the winter months.
“There are a variety of methods used to control HWA including pesticides, silvicultural treatments, and imported biological controls, but no single method will be sufficient alone,” said Melody Keena, research entomologist with the USDA Forest Service Northern Research Station in Hamden, Conn., and study co-author. For example, landscape trees are accessible and easy to treat with pesticides, while trees in forest settings are more difficult to treat.
“Developing silvicultural treatments to enhance hemlock survival, developing HWA tolerant hemlocks and building a greater range of biocontrol agents that are effective over the generations of the insect are all areas ripe for future research in the battle against HWA,” said Keena.
Pheromone Blend Draws More Bugs
Emerald ash borer may get more press, but there are other non-native, wood-boring insects in line behind them that have the potential to threaten United States forests, and the faster land managers can locate them, the less time they have to settle in and establish populations. Traps baited with pheromones – chemicals insects emit to elicit particular responses from other insects – are an effective tool in early detection of non-native species, unless you have to use separate traps for every species you want to track. Research Entomologist Therese Poland and her colleagues found that the right blend of pheromones makes it possible for land managers to place (and routinely check) a few traps with different blends of pheromones that are attractive to multiple invasive species.
The idea of developing a blend of pheromones to draw several insects to the same trap originated with the observation that even when a trap is baited with pheromones specific to a certain species, researchers always find a scattering of other insects. “We thought, why not play around with pheromone blends and see what would draw the most species?” Poland said.
When they analyzed pheromones for specific wood-boring insects, Poland and her colleagues, Larry Hanks and Jocelyn Millar, found that many related beetles share common components in the chemical makeup of pheromones. “They evolved from common ancestors, so it makes sense that they would still have some commonality,” Poland said. “While the pheromone components of one species might attract or at least have no effect on another species, others inhibit certain species, so our challenge was to find what blend of pheromone draws the most species and discourages the fewest.”
Traditionally, insect traps have been used in areas most at risk to invasion by non-native species, such as woodlots near ports or industrial warehouses. Traps were often attached to a pole and stuck in the ground near a tree, a technique that researchers now know limits the effectiveness of the trap. Positioning traps at different levels of the tree allows foresters to more accurately gauge the presence of insects in the tree’s canopy, the trunk, or anywhere in between. “Different insects depend on different parts of a tree during their lifecycle, so to know what is out there, you need to trap at different heights,” Poland said.
Like all research, Poland’s study seems sudden and certain, but in reality it is the result of a decade of questions, experiments, and more questions.
Agencies Collaborate on Tools to Manage Asian Longhorned Beetles
One group of scientists and land-managers had data, a lot of data. A Northern Research Station scientist had expertise in turning data into useful applications. That was enough to inspire an informal but lasting partnership among researchers and land-managers with the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) and the USDA Forest Service Northern Research Station.
It started when scientists with Penn State, the Forest Service, and APHIS were researching development of pheromone traps for Asian longhorned beetles (or ALB), a non-native insect that could threaten several species of trees native to the Northeast and Midwest. Finding infested trees requires intensive surveys for small holes on trees, and traps may ultimately provide an additional way to check the landscape.
Talbot Trotter, a research ecologist with the Northern Research Station, joined the group to help assess the effectiveness of the traps using infested-tree data collected by the APHIS ALB Eradication programs. The volume of data collected by APHIS crews inspired a vision for using it to track the progress of ALB in the three locations APHIS was monitoring: Worcester, Mass., New York City, and Bethel, Ohio, and a new research partnership between the Forest Service and APHIS emerged.
The partnership led to development of a set of tools that allows APHIS researchers to continually refine their search for ALB by using new data to recalibrate models showing risk of ALB movement. “Working as a team made a phenomenal difference to our ability to monitor a highly invasive insect,” said Ryan Vazquez, program director for APHIS’ Massachusetts ALB Cooperative Eradication Program. “The ability to integrate new data gives us a more reliable tool showing where the next hot spot might be located.”
Over the past 4 years, the Northern Research Station’s partnership with APHIS has survived the staff changes that often doom informal partnerships; scientists and managers have even coauthored research papers together. “This has been a great opportunity to show how different agencies of the U.S. Department of Agriculture collaborate on something that benefits land managers and advances research,” Trotter said.
For Trotter, the APHIS data on ALB movement was a research treasure-trove showing the distance and direction ALB traveled based on 15,000 trees in Worcester, New York City and Bethel. He found that the three different beetle populations have very different patterns of movement. For example, in Worcester, ALB generally move toward the northeast and southwest, while in Bethel they move northwest and southeast.
“It’s fun to see the patterns because then you get to ask 'why?'” Trotter said.