Field Notes: Fighting the Hemlock Woolly Adelgid on State Forests

By Lori Chamberlin, VDOF Forest Health Manager

Hemlock trees have been under attack since the introduction of the hemlock woolly adelgid, an invasive insect that was first discovered in eastern North America in the 1950s. These small insects settle at the base of hemlock needles, feed on plant sap, and surround themselves in soft, white ovisacs that resemble cotton balls. They may look harmless, but the hemlock woolly adelgid has caused widespread hemlock mortality in eastern North America. To fight back, the VDOF forest health program has implemented a variety of control techniques to protect remaining hemlocks on State Forests in Virginia.

Hemlock woolly agelgid on hemlock branch

When applied correctly, chemical control is very effective and can protect a hemlock tree for many years. In April, VDOF forest health staff and Shenandoah work area staff treated over ninety hemlock trees at First Mountain State Forest and over thirty trees at Paul State Forest. The hemlocks at both forests are infested with the hemlock woolly adelgid, but are in relatively good condition. A systemic insecticide was applied as a soil drench around the base of each tree; it will be taken up by the roots and distributed throughout the tree to provide protection for up to seven years!

Katlin DeWitt, VDOF forest health specialist, applying insecticide as a soil drench at First Mountain State Forest

Biological control is another method with the potential to provide long-term protection. All biological control agents are studied at quarantine facilities before they are approved for release, to ensure that they will not affect non-target hosts. Predator beetles (Laricobius spp.) have been released on public lands for many years, but this year VDOF participated in the release of a new biocontrol agent- silver flies. The larvae of Leucopis argenticollis silver flies prey on the eggs of hemlock woolly adelgid. In March, 435 adult Leucopis argenticollis flies from the NYS Hemlock Initiative’s HWA Bio-Control research lab at Cornell University were released at Sandy Point State Forest. We hope that these flies will establish a population and help control the hemlock woolly adelgid at Sandy Point for many years.

Field Notes: EAB-Killed Ash – Use It or Lose It!

By Joe Lehnen, VDOF Forest Utilization & Marketing Specialist, and Katlin DeWitt, VDOF Forest Health Specialist

The emerald ash borer (EAB) is an invasive beetle that has decimated native ash trees. It has been present in the U.S. since the late 1990s, feeding on and killing ash in Virginia since initial detection in 2008. This insect is native to Asia and most likely arrived on imported wood packaging material. While named for the metallic green coloring of the adult, it’s the white, segmented larva that destroys the tree by feeding under the bark on the tree’s vascular tissue. This feeding disrupts the movement of water and nutrients within the tree. The ‘S’-shaped feeding galleries the larvae create dry out the inner tissue and make it very brittle. As the tree dies over a two- to three-year period, it continually loses moisture content, becoming drier and more brittle with each passing month.

EAB adult shown with larval galleries

Symptoms and stress responses from EAB feeding include epicormic sprouting (sprouts coming out of the trunk from dormant buds), crown dieback, woodpecker stripping (they love to eat the larvae!), and ‘D’-shaped exit holes on the bark from where the adults emerge.

Currently, EAB has been confirmed in most counties in Virginia. There are just a few counties in the southeastern part of the state where we have yet to find any life stage of this beetle to send to the State Entomologist for official confirmation.  In areas like northern Virginia and Southside, where EAB has been present for over a decade, most trees that were not chemically treated are now dead. (Visit this interactive dashboard for more information.) In areas where the infestation is still ongoing, some trees will look outwardly healthy but have symptoms of decline. There is typically a lag period from when the beetles first infest an ash to when symptoms begin to show, making it important to plan ahead to treat or remove your tree before it dies! While ash species only makes up about 2% of all forested volume in Virginia, this still comes out to an estimated 187 million ash trees across the state. Additionally, this species can be found in high concentrations in urban and riparian areas, meaning that loss of these trees has a greater localized impact.

Declining ash trees, a common sight in Virginia

Tree fellers have relayed stories about the branches of dead ash breaking and falling as the trees are being cut, or the entire crown “exploding” as it hits the ground. Without question, there must be increased safety awareness when felling EAB-killed ash. Most arboriculture companies will not allow their personnel to climb a dead ash to begin the felling process.

In a recent project at Camp Kum-Ba-Yah in Lynchburg, VDOF personnel assisted local arborists with an ash removal project. While the arborists dismantled the trees near structures, VDOF sawyers felled the dead ash located in the woods that were adjacent to trails and other remote recreational facilities. Most all of these ash did not leaf out in 2020. VDOF project leader Bill Perry indicated that only smaller branches (2” or less) broke apart when the tree hit the ground. He also noted there was no breakage or cracking of the trunks. Bill also provided the following advice when felling these dead ash trees: “I was skeptical of using an open-face notch (90 degree) and leaving a heavy hinge. The trees are very quick to split up the trunk. Using a 45-degree face notch and a stump shot with a thinner hinge was giving me good results. I was not heavy wedging any of the trees for fear of wood quality.”

Ash trees killed by the EAB can still make a quality lumber product. The main takeaway is to mill these dying/dead trees as soon as possible for two reasons: the safety of the tree feller, and the integrity of the wood. Also remember that the EAB is not a deep boring insect. Most of the damage done by EAB activity is removed as the outside bark slabs are sawed from the log. If you’re searching for a portable sawmiller to process ash logs, check out the Urban and Small Woodlot Forestry Business Directory, where over 45 are listed.

Portable sawmill

Scientists are working hard to help protect ash in the long term. Researchers at the USDA Forest Service are working on studying the genetics of seemingly resistant trees. There are also national seed collection banks that are collecting seeds of all ash species, in order to preserve a seed source to replant the landscape once the first wave of EAB attack has subsided. In the meantime, VDOF is working to treat as many ash trees as possible with insecticides and to release small, host-specific wasps (harmless to humans) to control EAB eggs and larvae. Collectively, the efforts of many are helping to preserve ash across the Virginia landscape.

Field Notes: (Hopefully Not) Spotting the Spotted Lanternfly

By Katlin Dewitt, Forest Health Specialist

The spotted lanternfly is an invasive, sapsucking insect that was first detected in Winchester, Virginia in January 2018. As a pest of many different plants, it poses a threat to many of our native tree species, such as black walnut, maples, cherries, and many more. Additionally, this pest feeds on numerous commercially important plants like grapes, hops, apricots, plums, and apples.

As a sapsucker, the spotted lanternfly utilizes piercing-sucking mouthparts to feed on sap from woody parts of plants. It takes in an excess of sugary material, which then must be excreted from its hind end. This material is called honeydew and sounds (and feels) like a sticky rain falling from the trees above when spotted lanternfly populations are high! Honeydew can be messy and attracts other problematic pests, like ants and stinging wasps, and also allows for the growth of sooty mold.

Spotted lanternfly adults on tree

One of the ways this pest has spread so far in a relatively short amount of time is through unintentional movement of egg masses on materials and goods. An adult female can lay up to two egg masses and each egg mass can contain 30-50 individual eggs! She will lay her egg masses on any flat or smooth surface protected from the elements; this may be on the underside of tree branches, underneath flaky bark, sides of picnic tables, scrap metal, or even children’s playsets! Egg Masses are quite cryptic in coloration, blending in with many natural elements. Due to their camouflaged appearance and the female spotted lanternfly’s ability to lay eggs on many different surfaces, these egg masses can accidentally be moved by humans transporting firewood, camping trailers, or moving anything that has been sitting outside for an extended period of time.

Spotted lanternfly egg mass on tree

In an effort to prevent the spread of the spotted lanternfly, the Virginia Department of Agriculture and Consumer Services (VDACS) has implemented a quarantine for Frederick County and the City of Winchester. In March 2021, this quarantine will expand to also include Clarke and Warren counties. Loggers who are working near these areas should perform self-inspections to make sure they aren’t spreading the spotted lanternfly to new areas.

The spotted lanternfly overwinters (survives the winter) in the egg stage. This makes February a good time to survey for this insect. The Virginia Department of Forestry’s forest health team, along with eight foresters located around the state, are conducting spotted lanternfly egg mass surveys at high-risk locations. These are sites that receive a lot of vehicle travel (e.g., rest areas, truck stops), areas where people bring outdoor goods and equipment (e.g., campgrounds, hiking trails), or where large amounts of goods are moved (near train tracks, big shopping areas). Since spotted lanternfly will lay eggs anywhere and everywhere, including high up in tree tops, binoculars are a great tool to utilize while doing these surveys. All site data is entered into a Survey123 app that will eventually be merged with VDACS survey data. Hopefully no new detections will be found during these surveys, but if an egg mass is found, early detection allows us to act quickly and remove any outlier populations.

Field Notes: January’s Least Wanted – English Ivy

By Ellen Powell, VDOF Conservation Education Coordinator

A brand new year brings a brand new feature to Field Notes! Each month, one of our posts will introduce one of Virginia’s “least wanted” – an invasive species that’s easy to spot at that time of year. It might be a plant, an insect, or a disease that’s impacting our state’s natural communities. We hope you’ll keep an eye out for the pest on your own property, treat or remove it when possible, and spread the word about it to your friends and neighbors.

English ivy in its typical juvenile form

January’s least wanted is probably familiar to everyone. Perhaps, like me, you used it as the base for your Christmas wreath. It’s English ivy (Hedera helix), and it’s easy to see why European colonists brought it here with them. Viewed objectively, ivy is an attractive evergreen groundcover and climbing vine. But it’s harder to be objective when you know the dark side of English ivy.

Ivy in suburban woodland

Ivy in forests reduces plant biodiversity. The plant is highly shade tolerant and can completely cover the forest floor, to the exclusion of native understory plants and tree seedlings. Vines may climb as high as 90 feet, meaning ivy can easily overtop trees, blocking photosynthesis, which eventually starves the tree. Ivy also weighs down branches, making trees susceptible to breakage and windthrow during storms. If all that wasn’t bad enough, ivy is also a host for bacterial leaf scorch, a disease that affects oaks and other native trees.

In yards, ivy creates problems for homeowners. Its sticky aerial roots adhere to surfaces and retain moisture, potentially damaging any structure it climbs. The sprawling vines create thick mats that may harbor rats, mosquitoes, and other unwanted pests.

If allowed to grow unchecked, English ivy will eventually undergo a Jeckyll-to-Hyde transformation. It reaches its adult form around ten years of age, if the vines have achieved sufficient height and sunlight. The leaves change shape, losing their lobes to become more ovate. More importantly, the plant begins to flower and produce fruit.

Adult form, with flower cluster, top left, and fruits

Ivy produces a lot of berries (technically, they’re drupes, for those of us who like nerd words), which are highly visible this time of year. The fruits are toxic if eaten by humans, and they’re thought to be mildly toxic to birds as well; but, given their availability as a winter food source, birds eat them anyway. The seeds germinate best when the pulp has been removed. Interestingly, one study showed the best germination from seeds that had been regurgitated by birds, but passing through a bird’s gut works, too. Either way, new seeds tend to be dropped wherever birds perch, and soon new vines are making for the canopy.  

If English ivy makes your least-wanted list, you can get rid of it with some good old manual labor. Whether you choose to eliminate or simply control ivy, don’t allow it to reach its adult, fruiting form. If the ivy is simply running along the ground, mowing it regularly can keep it under control. Even better, remove vines by pulling them up, which is easier when the ground is moist. Be sure to wear long sleeves and heavy gloves; English ivy is NOT related to poison ivy, but the vines can cause contact dermatitis in some people. Pull climbing vines away from the base of trees or structures and clip every stem. Don’t try to rip vines off the whole tree, as you’ll probably remove a good deal of bark along with the ivy. Just be patient – the entire plant above the cuts will die back, eventually turning brown and losing leaves.

Unfortunately, none of these control tactics is a one-and-done solution. The plant will resprout from the roots, or from nodes of ground-running vines. Complete control can take years in some cases. English ivy’s waxy leaves are resistant to herbicides. If you choose to use a chemical, make sure you get a product recommendation from your local Extension Office or from the USDA Forest Service’s A Management Guide for Invasive Plants in Southern Forests.

Ivy in neighborhood common area

Unfortunately, ivy is still sold in nurseries. Given its prevalence in the landscape, you probably won’t have to look far to find an ivy infestation – tree trunks covered in green really stand out in the winter woods. Ivy is often obvious in neighborhood common areas – the wooded strips between home sites. How about a new year’s resolution to remove ivy from your property? If you spread the word about ivy’s downsides, maybe your homeowners’ association will follow suit.

On the Wings of a Tiny Wasp

The fate of Virginia’s stately ash trees might rest on the wings of a tiny wasp.

For more than a decade, ash trees (Fraxinus genushave been under threat from an invasive insect pest, the emerald ash borer (Agrilus planipennis) – EAB, for short. The larvae of this beetle feed on the phloem of ash trees, disrupting nutrient transfer. Native ash trees didn’t evolve with EAB, and its natural enemies aren’t here to control it. As a result, EAB has steadily decimated ash trees across much of the state, and an estimated 99% of our ash trees will die without some intervention.

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Efforts to protect individual valuable ash trees often involve treating them with systemic insecticides. But a landscape-scale approach is needed to protect forest trees. Enter the wasps – specifically, the tiny parasitic wasps that keep EAB in check in its native range – also known as “parasitoids”. There’s no need to worry about stings from these wasps. They use their ovipositors to lay eggs in or on EAB eggs or larvae – not to sting. Plus, they’re tiny. In fact, you might mistake them for gnats!

Three species of parasitoids have been intensively researched by USDA and approved for release in Virginia. They attack only EAB, so the hope is that they will establish populations here and keep the EAB population in check, allowing ash seedlings to survive and the ash population to regenerate in the future.

Release of parasitoids is a form of biological control, also known as “biocontrol.” In Cumberland and Whitney State Forests, VDOF has released thousands of wasps: Oobius agriliSpathius agrili and Tetrastichus planipennisi. So far, a survey of felled and debarked trees from Cumberland State Forest has revealed that some Spathius wasps have parasitized EAB larvae. (Incidentally, nearly a third of the EAB larval tunnels studied had been terminated by woodpecker feeding – an unintentional form of biocontrol!)

In addition to efforts in Cumberland State Forest, VDOF worked with land managers in Grayson Highlands State Park and James Madison’s Montpelier to release parasitoids (Oobius agrili and Tetrastichus planipennisi). The parasitoid biocontrol efforts support VDOF’s “100-themed” goal of protecting 100 ash trees across the state – part of the National Association of State Foresters’ Centennial Challenge. Although the 100 trees in the Challenge are being directly protected by insecticides, biocontrol has the potential to protect many more generations of ash trees.

It will take time to verify how well the wasps are controlling EAB populations. At Cumberland State Forest, they have made a start, and VDOF will assist land managers at Grayson Highlands State Park and Montpelier to monitor the impact on their properties.

Note: The parasitoids were produced and supplied by the USDA EAB Parasitoid Rearing Facility in Brighton, MI.

Saving Pumpkin Ash

In late May, Lara Johnson and Meghan Mulroy-Goldman (VDOF urban & community forestry team), along with the Virginia Beach Urban Forestry Department, embarked on a scouting mission for the rare pumpkin ash in the bottomlands surrounding Stumpy Lake in Virginia Beach (based on information shared from the Virginia Department of Conservation and Recreation.)

After traveling through the swampy coastal forest, Lara, Meghan and the Virginia Beach Urban Forestry Staff located nine healthy trees that will be treated this summer to protect them from emerald ash borer.

Pumpkin ash is a rare species, named for its swollen, pumpkin-shaped buttress. VDOF is thankful to the City of Virginia Beach for helping to preserve this species. With the treatment of these pumpkin ash in Stumpy Lake, VDOF will have helped to conserve populations of species of native ash within the genus found across the state. Protecting biodiversity is important for Virginia’s forest landscapes.

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This story is shared as part of VDOF’s participation in the NASF Centennial Challenge, in which VDOF has agreed to treat at least 100 ash trees to protect them against the invasive emerald ash borer.

AlterNATIVES

In Virginia, you know spring is just around the corner when you begin to see blooms on cherry, magnolia, pear, redbud and dogwood trees.

These same signs of spring can serve as a reminder that it’s a good time to assess the plants growing on your property and make a plan to get rid of the invasive species.

Non-native invasive plants usually have rapid reproductive rates, lack natural control agents and out-compete native species — that is, they can completely take over a landscape!

There are numerous invasive plant species in Virginia, ranging from grasses and vines, to shrubs and trees. The Virginia Department of Conservation and Recreation Natural, Heritage Division maintains a list of plant species that pose a threat to the Commonwealth’s forests, native grasslands, wetlands or waterways.

Four significant species that are common throughout the southeastern U.S. are tree-of-heaven, Japanese honeysuckle, Chinese privet and Callery (or Bradford) pear. You can read more about each species on these factsheets.

tree of heavenhoneysuckle
privet
bradford pear

Removing invasive plants often requires substantial effort and patience, but the reward is a natural area composed of diverse native plants. If you are successful in eradicating invasive plants on your property, congratulations! But what’s next? The work does not stop there. Now it’s time to replace the invasive species with native alternatives. Without planned replacement, those pesky invasive plants may just creep back onto your property.

Check out the AlterNATIVES factsheet for native alternatives that will keep your yard beautiful and the planet healthy!

alterNATIVES

These factsheets were created by the Southern Group of State Foresters, Forest Health Committee.

Field Notes: Looking Down on Tree of Heaven

By Katlin Mooneyham and Lori Chamberlin

The City of Winchester and Frederick County are in the midst of an invasion. The spotted lanternfly, a non-native invasive insect, was first discovered in Winchester in January 2018. This pest feeds on more than 70 host plants worldwide and poses a significant threat to multiple Virginian industries. There is still much to learn about the spotted lanternfly, and the Virginia Department of Agriculture and Consumer Services (VDACS) has been working hard to control it within the infested areas.

One method of slowing the spread is treatment of a preferred host, Ailanthus altissima, otherwise known as “tree of heaven”. Smaller trees are killed with herbicide and larger trees are treated with insecticide to kill spotted lanternfly that feed on them. Tree of heaven itself is an invasive species and is widespread throughout Virginia, especially along roads or other disturbed sites.

Knowing the precise location of tree of heaven would greatly facilitate treatment, so Virginia Department of Forestry (VDOF) partnered with VDACS to map tree of heaven in Frederick County and the City of Winchester. The project is supported by Farm Bill funds awarded to VDACS and accomplished with U.S. Forest Service software (Digital Mobile Sketch Mapper). Protocol was based on a 2015 Forest Science paper entitled “Aerial Detection of Seed-Bearing Female Ailanthus altissima: A Cost-Effective Method to Map an Invasive Tree in Forested Landscapes”, and personal communication with forest health professionals from the Pennsylvania Department of Conservation and Natural Resources. This type of survey requires a helicopter in December/January after leaf drop. Female tree of heaven hold onto their seed pods and are visible from above during these winter months.

VAsurveyTOH
Female tree of heaven trees from above (identified by attached brown seed pods).

In January 2020, VDOF forest health staff went up in a helicopter to map tree of heaven. The survey followed pre-determined flight lines spaced at 2,000 feet (1,000 feet of visibility from either side of the helicopter) and flew at an average altitude of 400 feet above ground at a speed of approximately 80 knots. Individual female trees were marked as points, and clusters of trees were marked as polygons. Three VDOF employees conducted the survey — two spotters and a sketch mapper — with minimal Dramamine needed for motion sickness!

Photos: VDOF staff Meredith Bean (emerald ash borer coordinator) and Katlin Mooneyham (forest health specialist) (left) and Jim Pugh (GIS technician) (right) ready for take off!

It will take some time to analyze the data and quantify the results, but general observations fit with our knowledge of this invasive tree species. Tree of heaven is most commonly found along disturbed sites and the highest numbers of trees were observed along train tracks, roadsides, field edges and a quarry in the southern end of the county.

Mapping female trees only gives us data for half of the population, but this winter survey is a quick and easy method to identify tree of heaven clusters to get a better idea of overall distribution. This data will be used by both VDOF and VDACS personnel to identify priority treatment areas and locate areas where the spotted lanternfly may continue to spread.

Paper Citation:
Rebbeck, Joanne, et al. “Aerial detection of seed-bearing female Ailanthus altissima: A cost-effective method to map an invasive tree in forested landscapes.” Forest Science 61.6 (2015): 1068-1078.

Field Notes: Yellow-Poplar Weevil Makes Presence Known in Southwest Virginia

by VDOF Forest Health Program Manager Lori Chamberlin

The yellow-poplar weevil has made its presence known again in southwest Virginia. This native insect generally causes very little damage, but the population increased enough this summer to have a noticeable impact on yellow-poplars in the southwest part of the state. The weevils are black and small, only about 1/8th of an inch long. Since this pest is a weevil, it has a long proboscis, or nose like appendage, that it uses to feed. Though their name implies they feed only on yellow-poplar, they also feed on magnolia and sassafras.

Adult yellow-poplar weevils emerge in early June and feed on leaves until mid-summer. As they feed, they make tiny notches shaped like a grain of rice in the leaf creating brown splotches on the leaf surface. This gives the trees a scorched appearance and may lead to premature leaf drop.

Since the yellow-poplar weevil is a native pest in the eastern United States, control is usually not warranted. Natural predators of the weevil normally regulate the population and keep it below damaging levels. Outbreaks of the weevil tend to occur every few years when weevil populations surpass natural predators. During outbreak years, tree damage may be unsightly and alarming, but is mostly just cosmetic and does not cause long-term harm to the trees. There have been six VDOF documented outbreaks in the last 25 years, all primarily in southwest Virginia. This year, reports of this pest came from Roanoke, Bedford, Buchanan and Russell counties. VDOF forest health staff conducted an aerial survey on July 2nd and mapped damage in Bedford, Botetourt, Roanoke, Montgomery and Floyd counties. Yellow-poplar weevil damage appears to be widespread throughout the western region this year, but it is patchy and scattered throughout the landscape.

In heavily infested areas, you may see these weevils crawling on top of vehicles or falling on people walking by. They are often mistaken for ticks, but don’t worry, the yellow-poplar weevil doesn’t harm humans!

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