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.
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!
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.
By Ellen Powell, VDOF Conservation Education Coordinator
With recent warm weather, Virginia’s woods are greening fast. After a dormant winter, plants gear up for photosynthesis again, using carbon dioxide, water, and sunlight to make food. You might be familiar with some early spring wildflowers that emerge on the forest floor, taking full advantage of the leafless canopy to gather some sun of their own before being shaded out by trees. Unfortunately, the shrub layer in many Virginia woodlands is full of some sneaky sun stealers – invasive plants.
Several of our most problematic invasive shrubs are among the first plants to leaf out in spring. What’s more, they often lose their leaves later than our native woody species. One study from Penn State estimated that invasive shrubs may get more than two months of additional growing time, when you add up their extra spring and fall leafiness. This gives the shrubs a competitive edge over native shrubs. Early leaf growth can also shade out understory plants that already have a pretty short window of opportunity to gather sun.
In March, the most obvious invasive shrub in the Charlottesville area is autumn olive (Elaeagnus umbellata). The silver-backed leaves give a pale green haze to many an understory, showing us just how prolific this shrub is. Soon after leaf-out, autumn olive’s sickly-sweet fragrance will permeate the woods, followed in summer and fall by silver-dotted red berries.
Chinese privet (Ligustrum sinense) is semi-evergreen in central Virginia, usually retaining a few winter leaves. By March, abundant new leaves are well on their way. Privet is another invasive whose flowers (in June) have a cloying scent and whose berries attract birds. In this case, the berries are dark blue and linger into early winter.
Multiflora rose (Rosa multiflora) is the prickly bane of many trailsides. It often grows in fairly shady areas, but this early leafer has little competition for sunlight in March. This shrub spreads not only from seed, but by spreading from the roots and stem tips that touch the ground. It can form dense thickets that are impossible to walk through without bloodshed.
Some of the bush honeysuckles (Lonicera spp.) bloomed in late winter, well before the leaves appeared, but the shrubs are greening up now. The related Japanese honeysuckle (Lonicera japonica) vine is mainly evergreen but puts on a flush of new growth in spring. Although evergreens may not actively grow in winter, some continue to put on root growth, and they are definitely ready to go earlier in spring than their deciduous neighbors. Other evergreen invasives include English ivy and wintercreeper euonymus.
You can learn more about invasive shrubs and vines from Blue Ridge PRISM’s fact sheets. PRISM stands for Partnership for Regional Invasive Species Management; this very active nonprofit uses education and hands-on efforts to stop the spread of invasives. VDOF’s Common Native Shrubs and Woody Vines also includes a “top ten” section of invasive species. Spring is the perfect time of year for learning to identify these pesky plants. Know them – DON’T grow them!
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.
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.
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.
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.
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 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.
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.
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.
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 genus) have 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.
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 agrili, Spathius 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!)
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.
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.
Last fall, a little seedling popped up in my yard. It was too young to be readily identifiable, so I left it on the off chance that it was something cool. This spring when it leafed out, I realized that it was a butterfly bush.
Now, I do not have any other butterfly bushes in my yard, but other folks in my neighborhood do, and this “volunteer” bush in my yard likely came from seeds spread from a neighbor’s yard. Aside from non-native butterfly bushes, my neighbors also have non-native Japanese barberry, burning bush, and Bradford pear that they care for and maintain as part of their landscaping.
Our choices for landscaping may seem innocent enough, but what we plant in our yards matters to our neighbors and our forests because plants like to spread. Some will spread through roots or rhizomes like mints, irises and tree-of-heaven. Others like sycamore, mulberry or cockleburs will produce seeds that disperse in the wind or will be spread by animals. In a yard with a mowed lawn and weeded flowerbeds, there may be few “volunteers” popping up, but downwind, downstream or along paths taken by wildlife, there may be many.
Why does this matter? Many of the plants that we plant in our yards and gardens are not native to this area (such as the plants in my neighbors’ yard mentioned earlier.) Plant species spend thousands of years developing important relationships within the place where they grow. This includes relationships between plants and pollinating insects, as well as with larger critters such as birds and deer. When we take a plant that has evolved to live in and contribute to its local ecosystem and replace it with a plant that’s native to an ecosystem halfway across the world, we disrupt many of these relationships.
Plants that do not have these developed relationships with the other native fauna are not as easily controlled because they have few natural predators. For example, deer like to eat the growing tips of native hardwood trees like oak seedlings, but they do not like to eat the tips of tree-of-heaven or Japanese barberry (both non-native, invasive species.) Therefore, when the seeds of these non-native plants disperse, there are no plant predators to slow their growth and spread. This contributes to the widespread infestation of private and public forestland with various non-native plants, some of which were first introduced in our landscaped yards. This is detrimental to forest health because these plants do not support important insects (think about pollinators!) and compete with native plants for resources such as sunlight and water.
There’s good news, however: you can help! As the weather warms and we focus on our gardens and landscape plans, I encourage you to take a moment to research what you are planting in your yard. For example, a quick Google search will show that butterfly bush is actually bad for butterflies, and local pollinators would be better served if you plant a spicebush or flowering dogwood. There are many trusted resources available to help folks find native plants that work with their landscaping, such as the Virginia Native Plant Society, which provides regional guides for the whole state.
If we bring native plants back into our yards and lives, we will be giving a helping hand to the many important insects and other critters that are so important for keeping our forests healthy and beautiful.
Although the butterfly bush was an undesirable discovery, I have also found yellow-poplar, flowering dogwood and sycamores in my garden that have spread there from trees in the neighborhood. Wouldn’t it be cool if instead of spreading harmful plants we could inadvertently spread lots of good ones?
The calendar and the plants agree – spring has arrived in central Virginia!
Patches of green among the leaf litter mean spring wildflowers are making their annual appearance. Often called “ephemerals,” for their short-lived bloom time, those in flower this week include pennywort (Obolaria virginica), star chickweed (Stellaria pubera) and wild geranium (Geranium maculatum).
Unfortunately, the shrub layer of many hardwood forests reveals a “dark side” of spring. Quite a few invasive plants green up earlier than native shrubs. These include wineberry, barberry, privet, multiflora rose and autumn olive.
The pale green plants in this picture are autumn olive (Elaeagnus umbellata), a non-native invasive shrub that often displaces the natural shrub understory. If you smell something cloyingly sweet while hiking, the culprit may be autumn olive in bloom. The tiny, tubular flowers will make way for red berries this summer.
A silver lining? The berries are high in lycopene and antioxidants, and they’re edible. So, pick as many as you can, before the birds spread them even farther!
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.
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!