invasive species

Select Ground Covers for Your Landscape Carefully

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Plants that are used as ground cover can provide great services throughout the landscape as they can fill in areas that might otherwise be left bare or covered in mulch. Ground covers can be used to help reduce maintenance chores by preserving moisture and preventing weeds. 

If you are looking for a ground cover plant, consider adding a native ground cover. Non-native ground covers and vines can be the plants of nightmares, as the characteristics that we like about them (aggressive, can take over weeds, need little care once established, etc.) are often the characteristics that make them terrible offenders when they escape into natural areas. A great field guide on this exact topic is Plant Invaders of Mid-Atlantic Natural Areas. 

Since it’s prime planting season in Maryland, here I highlight three herbaceous plants that are often used as ground covers that can quickly take over. For a more detailed list of some of the other ground covers that are concerning, check out this webpage, Invasive Vines and Groundcovers.

a covering of English ivy under a tree
near a forest edge English ivy is all over the ground and climbing up trees
English ivy (Hedera helix). Photo: M. Talabac, University of Maryland Extension

English ivy (Hedera helix) is sometimes just called “ivy” or “European ivy”, which reiterates the point that it is not a plant that is native to the United States. This evergreen, vining plant is one that you should be aware of as it can take over areas through the spread of seeds and through underground stems. It thrives in shade, is drought tolerant, and once established, it creates a thick, dense mat of foliage that can outcompete many perennials. It’s even been reported that it can damage homes/walls where it grows up and even penetrates the bark on living trees and strangles them. A study done in February of 2021 found that there are at least 5,000 trees in Takoma park could be lost because of English ivy. English ivy also serves as a reservoir for bacterial leaf scorch, a disease in maples, oaks, and elms.

For more information on English ivy, visit these webpages from the University of Maryland Extension: English Ivy and Invasives in Your Woodland.

Periwinkle (Vinca minor) close-up of purple flowers (left), and spreading along a staircase in Great Falls Park (right). Photos: M. Talabac

Periwinkle is a common plant that many people will recognize by its attractive shiny green leaves and purple-white flowers. There are actually two types, Vinca minor and Vinca major, unfortunately, both are considered invasive species and spread quickly vegetatively by root pieces (digging) and rooting at tips and nodes that contact the ground.

The third plant is bishop’s weed or goutweed (Aegopodium podagraria). Once established, this plant easily gets out of hand and is very difficult to remove. It is on the Maryland Department of Agriculture’s list of plants considered for regulation. Joyce Browning with the University of Maryland Extension in Harford County recently posted a video about bishop’s weed.

It can be overwhelming when considering adding plants in troubled areas. A great resource for ideas is the University of Maryland Extension webpage about Lawn Alternatives. 

Remember that you can help mitigate the negative effects of invasive plants on local ecosystems by not adding them to your landscape. However, if you already have some of these plants, you can also manage them correctly by keeping them contained in certain areas and eliminating their spread into natural areas. Never place yard trimmings into natural areas, and remove the seeds before they can be spread by wind, rain, and/or animals. As you are adding plants to your landscape, please check out these great resources for non-invasive plant suggestions: 

Landscaping with Native Plants- Maryland Native Plant Society 

Keystone Plants by Ecoregion- National Wildlife Federation

Resources on invasive plant identification: 

Plant Invaders of the Mid-Atlantic Natural Areas (PDF)

Do Not Sell! Ornamental Invasive Plants to Avoid with Climate Change (PDF)

Everyone can help in the fight against invasive plants! Check the University of Maryland Extension website for an Introduction to Invasive Plants in Maryland and more information on how to reduce them. The absolute best way is to just never plant or introduce them into your landscape. 

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.

Nurture Natives: 4-Hers Take a Stand to Protect Maryland’s Ecosystems, Economy, and Agriculture

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This is a guest post by Esther Bonney, a student in Charles County, Maryland, and a member of the University of Maryland Extension 4-H Program.

Invasive plants are detrimental to Maryland’s well-being, and their damaging effects are becoming more evident each year as we witness declines in crop productivity, reductions in pollinators critical to maintaining stable ecosystems, and widespread displacement of native habitats. Between 2008 and 2013, wild bees declined by 23 percent across the U.S.—a serious concern to farmers and consumers alike. Through educational programs, guides, and native giveaways, Nurture Natives is taking a stand against invasive species to protect native plants and pollinators, restore natural habitats, and support farmers. Nurture Natives is led by University of Maryland 4-Hers Esther Bonney and Samantha Rutherford and Extension 4-H Educator Amy Lang and UME Charles County Master Gardener Marlene Smith. 

people line up for native trees at Maryland Day
Visitors line up for native trees at Maryland Day, stretching down the courtyard and around the sidewalk, sometimes longer than the line for free ice cream!

In March 2022, our team was selected to attend the National 4-H Youth Summit on Agriscience. There, we developed our project, Nurture Natives, to address a prevalent agricultural issue in our community: invasive plant species. Invasive plants choke out native species and are a major cause of crop loss and food insecurity. Invasive trees such as the Tree of Heaven rapidly overtake farmlands and attract invasive pests such as the Spotted Lanternfly, which is a serious threat to grape crops. In the U.S. alone, invasive species cause $40 billion worth of production losses to crops and forests per year. 

Nurture Natives is dedicated to increasing biodiversity through the planting of native trees and the eradication of invasive plants. In the past year, Nurture Natives has been featured on the National 4-H and University of Maryland Extension websites, won a Lead to Change Grant, and was selected by the National 4-H Council as one of two projects nationwide to receive the highly-competitive Scale for Success Award. Nurture Natives was also recently featured in the Southern Maryland Independent: Nurturing natives and the next generation of environmental scientists. 

Our team began our work by educating and raising awareness about invasive species in our community of Charles County. We hosted educational programs at schools and camps and, in October 2022, partnered with eight local organizations to host the first annual Nurture Natives Giveaway. We hosted games, crafts, presentations, and a honey-tasting to showcase the importance of native species and pollinators. In just two hours, we distributed 150 native trees and shrubs and reached over 70 families. 

Samatha at the Maryland Day tree giveaway
Marlene taking forms at the tree giveaway
Samantha Rutherford (left) hands out trees to visitors at Maryland Day, and Marlene Smith (right), Charles County Master Gardener, collects forms from patrons before they reach the tree distribution table.
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Invasive Shrubs With Red Berries to Avoid

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Blooming flowers, emerging leaves, sprouting seedlings, and peeping frogs are just a few of the signs that encompass the magic of the spring season for me. As nature goes through the motions and awakens, I hope you have found some time to get outside and enjoy the wonderful gift of the changing seasons. Unfortunately, I’m always disheartened to see the number of invasive shrubs that are dotting the landscape this time of year. Spring is an easy time to see firsthand how invasive plants often break dormancy before native plants, which basically means that they leaf out earlier and have an automatic leg up as they are growing a few weeks before other plants. For more information, read Invasive Shrubs in Northeast Forests Grow Leaves Earlier and Keep Them Longer from Penn State. 

an invasion of bush honeysuckle plants covering a forest floor
Bush honeysuckle shrubs taking over a forest understory. Photo: Troy Evans, Great Smoky Mountains National Park, Bugwood.org

Q. What shrub has yellow-white (sometimes pink), trumpet-shaped flowers in mid-spring that smell sweet? 

A: Exotic bush honeysuckle is a large category of several different fast-growing species (Lonicera maackii, L. morrowii, L. tatarica, L. xbella, L. fragrantissima) that are perennial, deciduous shrubs that can grow up to 20 feet in height. These species share many of the same characteristics — yellow to white, sometimes even pink-colored flowers, sweet-smelling flowers, and red to yellow berries in early summer. Leaves are opposite on the stem. Wildlife such as deer and birds are known to spread these invasive shrubs by eating the berries. If you look underneath utility lines or at the forest edge, you will often see these invasive shrubs.

As of February 2018, the Maryland Department of Agriculture classified Amur honeysuckle (Lonicera maackii) as a Tier 1 invasive plant in Maryland. A person may not propagate, import, transfer, sell, purchase, transport, or introduce any living part of a Tier 1 invasive plant in the state. For more information visit the University of Maryland Extension page about Exotic Bush Honeysuckles. For control information, visit Invasives In Your Woodland: Bush Honeysuckles.

multiple white and yellow flowers of bush honeysuck
Bush honeysuckle flowers. Photo: Ryan Armbrust, Kansas Forest Service, Bugwood.org
multiple red berries on a bush honeysuckle shrub
Red fruits of bush honeysuckle. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Over the last 5 years, I’ve seen a huge increase in the number of invasive shrubs in my own woodlot, which is secluded from homes due to the mountainous terrain. Nonetheless, Japanese Barberry (Berberis thunbergii) has begun taking over the understory and edges of hayfields. I believe that it was spread by wildlife. Did you know this shrub gets small yellow flowers in early spring and then red berries?

yellow flowers of Japanese barberry
Japanese barberry flowers are yellow. Photo: Miri Talabac, University of Maryland Extension
red berries of japanese barberry
Japanese barberry fruits. Photo: Richard Gardner, Bugwood.org

Q. I see Japanese barberry planted in many landscapes. Is it really an invasive plant?  

A: This invasive shrub has been used in landscapes in North America since the late 1800s. It is very popular because it provides resistance to deer browse and can grow in a wide variety of light and soil conditions, making it a plant that can be used dependably in home landscapes. However, these characteristics contribute to its aggressive nature when spreading into natural areas. It forms dense foliage thickets that create an ideal humid environment for black-legged ticks (deer ticks) which can carry the pathogen that causes Lyme disease.

The Maryland Department of Agriculture (MDA) has named this a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. Landscapers may not supply Japanese barberry unless they provide the customer with a list of Tier 2 invasive plants. In our neighboring state of Pennsylvania, Japanese barberry is on the noxious weed list and will be banned for sale beginning this fall.

Visit the University of Maryland Extension website for more information about Japanese barberry and how to control it.

Japanese barberry infestation in a forest. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Q.  I want to add a shrub to my landscape that provides berries for the wildlife and fall foliage color. Is burning bush (Euonymus alatus) a good choice?

A: Unfortunately, winged burning bush (Euonymus alatus) is not the best choice when adding a new shrub to your landscape, as the Maryland Department of Agriculture (MDA) has named this a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. Landscapers may not supply winged burning bushes unless they provide the customer with a list of Tier 2 invasive plants. It is also important to note that burning bush is now a banned noxious weed in our neighboring state of Pennsylvania.

For more information, check out this previous blog post, Q & A: Is Burning Bush an Invasive Plant? For control suggestions, refer to Invasives in Your Woodland – Winged Euonymus.

leaves of burning bush
Burning bush branch. Photo: Richard Gardner, Bugwood.org
red berries of burning bush
Burning bush fruits. Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Q. Does Heavenly bamboo support wildlife with its evergreen leaves and red berries? 

Heavenly bamboo, sacred bamboo, or Nandina (Nandina domestica) has berries that are actually toxic to cats and also cedar waxwing birds. This plant was introduced from Asia in the early 1800s but it outcompetes many native plants with its aggressive nature.

MDA has named Nadina a Tier 2 invasive plant. This classification means retail stores that offer this plant for sale must display a required sign indicating that it is an invasive plant. The Nandina cultivar ‘Firepower’ is the only exception.

For more specifics about this plant, read Not so Heavenly from the Maryland Invasive Species Council. The Master Gardeners of Northern Virginia have a good list of native alternatives to plant instead.

Invasive heavenly bamboo (Nandina domestica). Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

All of these invasive shrubs produce berries which is one of the ways they spread so widely and easily. Please research plants before adding them to your landscape. Below are links for information on finding non-invasive plants: 

Native Shrubs – University of Maryland Extension

Landscaping with Native Plants- Maryland Native Plant Society 

Keystone Plants by Ecoregion- National Wildlife Federation

Resources on invasive plant identification: 

Plant Invaders of the Mid-Atlantic Natural Areas (PDF)

Regional Invasive Species & Climate Change Management Challenge: Do Not Sell! Ornamental invasive plants to avoid with climate change

Check the University of Maryland Extension website for an Introduction to Invasive Plants in Maryland for more information on how to reduce them.

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.

Invasive Trees in Maryland: Princess Tree, Callery Pear & Tree-of-Heaven

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Last month, my blog post was an introduction to invasive plants and today I want to share information on three invasive, deciduous trees found in Maryland. 

Springtime provides a breathtaking display of contrasting flowers in a wide array of colors, shapes, and sizes, which are found in herbaceous plants, as well as woody shrubs and trees. Unfortunately, some of these spring flowering trees are invasive and you need to be aware of their negative effects on ecosystems such as competition for resources including sunlight, soil nutrients, and space.

Q: What medium-sized invasive tree has white blooms in the early spring in Maryland?

invasive callery pear trees crowded along a road
Callery pear (Pyrus calleryana) in flower. Photo: Britt Slattery, US Fish and Wildlife Service, Bugwood.org

Callery Pear (Pyrus calleryana), sometimes referred to as ‘Bradford’ Pear, has several cultivars including ‘Chanticleer,’ ‘ Cleveland Select’, and ‘Autumn Blaze’, all of which will be in bloom around this time of year. The Callery pear was imported from Asia to Maryland with the hope of being able to help edible Bartlett pears, which were being threatened by a disease called fire blight. The plan was to cross these pears to gain disease resistance in the pear industry. Unfortunately, this experiment was unsuccessful in preventing fire blight, but these crosses seemed to have potential for the ornamental industry and were planted widely. Bloom time often coincides with our native serviceberry, which produces white flowers too.

The ‘Bradford’ cultivar was thought to be sterile; however, when new cultivars of Callery pear were developed, it was able to cross-pollinate with those and produce viable seeds. Birds and other wildlife eat the fruits, which results in spreading them to different areas. The seeds sprout and grow into dense thorny thickets, which are very difficult to control and result in crowding out native vegetation. Callery pear provides a stunning show of beautiful white blossoms; unfortunately, these trees are highly invasive, which has led a few states to ban all cultivars of Callery pear (Pennsylvania, Ohio, and South Carolina). This tree has an attractive V-shaped crotch that unfortunately will often split from high wind and snow weight damage. 

For more information, history, and control options, please visit the University of Maryland Extension webpages: Invasives in Your Woodland and Bradford Pear.

Q:  What invasive tree has purple blooms in early spring?

lavender flowers of princess tree

Princess Tree (Paulownia tomentosa). Photo: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org

Paulownia (Paulownia tomentosa), also called princess tree or empress tree, has purple, pleasant-scented blooms that appear before the foliage in early spring. I saw this tree for the first time when I traveled to Howard County for training in 2012, as this is not a tree we have in Garrett County. Its striking, large, heart-shaped leaves automatically caught my attention and reminded me of the Northern catalpa tree, a great native tree that should not be mistaken for Paulownia. According to Plant Invaders of the Mid-Atlantic Areas, one empress tree is capable of producing 20 million seeds that mature to flowering in only 10 years! These trees prefer full sun but can grow on disturbed soils, creek banks, and even forested areas which gives them a big advantage over native species that often require more special environments to grow and thrive. Paulownia’s ability to sprout from adventitious buds on stems and roots allows it to survive fire, cutting, and bulldozing. It is, therefore, a very difficult and costly invasive plant to control, according to the Maryland Invasive Species Council Plant Invader of the Month listing. 

A great alternative to Paulownia is the native Eastern redbud, which produces early, purple/reddish-purple blooms. 

For additional information, history, and control options for Paulownia, visit the University of Maryland Extension web pages Invasives in your Woodland and Princess Tree. 

Q: What invasive tree looks similar to black walnut?

tree of heaven foliage looks very similar to that of black walnut and sumac
Tree-of-Heaven (Ailanthus altissima). Photo: Chuck Bargeron, University of Georgia, Bugwood.org

Tree-of-Heaven (Ailanthus altissima) was introduced in the late 1700’s and thrives in many soil conditions. It has an amazing ability to grow very quickly and can disturb building foundations and even pavement! It was widely planted as a street tree and thus is found far and wide in the Eastern United States. This tree is called by other names including China-sumac, stinking sumac, or varnish tree due to its strong unpleasant odor. Tree-of-Heaven is sometimes mistaken for sumac, hickory, or black walnut because of similarities in leaf shape; however, look for the glands on the bottom of each leaflet to confirm its identity. 

Just in case you needed one more reason to remove Tree-of-Heaven, it is a preferred food source for the new, exotic, invasive insect pest, spotted lanternfly.  

For more specific information, history, and control options, visit these web pages:

Keep an eye out this spring for non-native, invasive trees as there are many others that I did not address in this article. Take any opportunity to help educate friends or family about the negative impact of invasive plants on biodiversity.   

Resources for invasive plant identification: 

Resources for non-invasive plant suggestions: 

Check out the University of Maryland Extension website on Introduction to Invasive Plants for more information on how to reduce invasive plants.

Remember, the absolute best way to avoid invasive plants is to never plant or introduce them into your landscape! 

By Ashley Bodkins, Senior Agent Associate and Master Gardener Coordinator, Garrett County, Maryland. Read more posts by Ashley.

Plant shopping soon? Avoid buying invasive plants

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It’s a sunny day in late February and that means I’m looking at seed catalogs and dreaming of new plants! Have you been plant shopping yet this year? Adding new plants and seeds to your garden creates new scents, textures, colors, and shapes and is the easiest way to increase biodiversity in your landscape!  

As you begin revitalizing your garden space this spring, I want to bring some attention to invasive plants, a category of plants that should strike fear and dread in your heart! Okay, maybe that’s a bit dramatic, but truly this is a topic that everyone needs to learn more about. 

Q. What is an invasive plant?

A. An invasive plant is a non-native, “alien” species that was introduced intentionally or by accident into the landscape and causes ecological and/or economic harm. These plants tend to be free from predators, parasites, and diseases that could help keep them in check. These plants reproduce rapidly with multiple methods (i.e. seeds, stolons, root cuttings, runners, etc.) and spread aggressively. They tend to be deer resistant or deer tolerant, a big reason why they are purchased and planted in landscapes. Below is a photo of purple loosestrife. Notice how it is creating a monoculture, a visual key that might mean the plant is “invasive.”

purple loosestrife flowers crowding a field
Invasive purple loosestrife (Lythrum salicaria).
Photo: Richard Gardner, Bugwood.org

Did you know that some invasives are still for sale at nurseries, greenhouses, and in mail-order catalogs?   

It’s true. Many of the plants on “watch lists” are still readily available to purchase. Japanese barberry is an invasive plant that is a very popular landscape plant still being widely planted today; however, research shows that black legged ticks have been found in areas with invasive barberry thickets because these non-native, invasive forest shrub thickets create ideal microclimates.   

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Look out for wintercreeper

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wintercreeper vines climbing up trees in a forested area
Wintercreeper euonymus (Euonymus fortunei) overrunning a woodland floor and climbing tree trunks. Photo: Ryan Armbrust, Kansas Forest Service, Bugwood.org.

Q:  I realize English ivy is widespread in Maryland, but there are some evergreen vines clinging to trunks that look a bit different than typical ivy leaves. Are they native, or should they too be removed?

A:  An evergreen climber I see covering tree trunks in parks which might be confused for English ivy at a distance is wintercreeper (sometimes written winter creeper; Euonymus fortunei). This non-native invasive acts like English ivy in that it’s a groundcover when no support to climb is present, and a clinging vine when trunks or walls are available.

wintercreeper vine
Wintercreeper vine. Photo: Chris Evans, University of Illinois, Bugwood.org
wintercreeper flowers
Wintercreeper flowers. Photo: James H. Miller, USDA Forest Service, Bugwood.org
wintercreeper berries
Wintercreeper fruits in December. Photo: James H. Miller, USDA Forest Service, Bugwood.org

This species also has negative impacts on the trees and our ecosystem and should be removed if growing on your own property. Parks manage invasives as best they can, but with limited resources, we can do our part by not cultivating the species likely to spread into them, even if we don’t live immediately next to parklands. Weed Warrior volunteer programs exist, such as in Montgomery County, if you wish to be trained in invasive plant ID and to help with their removal on public lands. While wintercreeper has been banned for sale by the Maryland Department of Agriculture since 2018 as a Tier 1 invasive plant, established plants in the region can still mature enough to produce fruit (berries) that wildlife then inadvertently spreads into natural areas. Long a popular landscaping groundcover due to those vibrantly green leaves (and the variegated forms for their color), I always recommend removal and replacement with alternatives, preferably a medley of native species instead.

As with English ivy, it’s safest for the tree to simply sever the climbing wintercreeper stems’ connection with the roots in the ground and let them slough off the trunk on their own as they dry out and disintegrate. Even though they attach via root-like structures, those aren’t functional roots and no moisture or nutrients are absorbed by them. Pull up, smother (deny them light), or spray any running stems covering the ground. As with any tenacious weed, eradicating an established patch of this species may take time and repeated efforts at removal before finally being successful. Be vigilant, because birds could always re-introduce it in a future year. (Invasive plants…the gift that keeps on giving.)

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

Have a plant or insect question? The University of Maryland Extension has answers! Send your questions and photos to Ask Extension. Our horticulturists are available to answer your questions online, year-round.

Spotted lanternfly: The latest invasive species spreading through the eastern U.S.

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A man is holding an adult spotted lanternfly to show its wings
Adult Spotted Lanternfly. Photo: M Raupp, UMD

¿Hablas español? Aquí esta una traducción: Mosca linterna con manchas: la especie invasora más reciente que se está extendiendo por el este de los Estados Unidos.

Spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), is an invasive planthopper moving its way through the eastern U.S. SLF was first detected in the U.S. in 2014 in southeastern Pennsylvania. It is native to parts of Asia and believed to arrive as egg masses laid on landscaping stones shipped to PA. Despite quarantines and eradication efforts, SLF infestations have been confirmed in 12 states and detected in several others.

A map shows that spotted lanternfly is confirmed in 12 states in the northeast USA
Since spotted lanternfly was first detected in Pennsylvania in 2014, confirmed infestations are in 12 states as indicated by this map (as of June 30, 2022). Image: https://nysipm.cornell.edu/environment/invasive-species-exotic-pests/spotted-lanternfly/spotted-lanternfly-range-us/

As we look at the SLF distribution map, we can see that counties with infestations are hundreds of miles away from any other infestation. This is related to the fact that SLF are excellent hitchhikers, taking advantage of human-assisted transportation. Many infestations occur along major interstates and train lines. In addition, the nymphs are active walkers and adults are able to hop and fly to new host plants and locations. Researchers at Penn State found that some SLF nymphs travel as much as 213 feet, and adult flights ranged from 30 to 150 feet in their search to find suitable hosts.

In response to SLF’s impressive ability to disperse, states have implemented regulatory quarantines and permitting programs implemented through State Departments of Agriculture, which requests actions be taken by businesses and the public who travel in and out of SLF-infested areas.

What do we know about the life cycle of SLF?

The life cycle of SLF consists of one generation per year, with eggs (the overwintering stage) laid in the fall (September – November). Egg masses are laid on smooth surfaces such as tree branches, landscape stones, rocks, wood from decks or fencing, outdoor furniture and equipment, etc. Egg masses are covered with a mud-like substance likely for protection. The protective covering is gray when freshly laid and becomes brownish with age. The eggs hatch in the spring between 240 (usually early to mid-May) and 1100 (late June to early July) degree days (DDs).

Spotted lanternfly egg mass ona tree trunk
Freshly laid egg masses of spotted lanternfly are gray in color and camouflage well on tree branches and other structures. Photo: M.J. Raupp, UMD

There are 4 nymphal instars (immature stages). Newly hatched nymphs are small (~1/8”) and at each molt they somewhat double in size. The first three nymphal instars are black with white spots and the last nymphal instar is red with white spots and black stripes.

early instar spotted lanternflies
Early instar spotted lanternfly nymphs are often found on new growth of plants. Photo: PA Dept. of Agriculture
late instar spotted lanternfly nymph
Late instar (4th) nymphs are about ½” long, bright red with white spots and black stripes. Photo: D. Ludwick, Penn State Extension
Spotted lanternfly adult
The adult spotted lanternfly has beautiful coloration and is ~ 1 inch in length. Photo: M.J. Raupp, UMD

In PA, adults begin to emerge in July (50% adult emergence at ~ 1,100 DDs) and they remain active (feeding, excreting honeydew, mating, and laying eggs) until the first hard freeze, which kills them. Adults of this planthopper are beautiful and relatively large (~1”). Adults have black bodies and legs; their front wings are gray with black spots and the ends are black with gray veins. Their hindwings are red, black and white. When the adult spreads its wings, the bright red color is quite impressive. Nymphs and adults are robust jumpers and adults can also fly.

Why is SLF problematic?

SLF is a voracious feeder on over 70 different plant species, which include numerous economically-important plants such as grapevines, some herbaceous ornamental plants, fruit trees, numerous ornamental trees, and tree of heaven. It uses its piercing sucking mouthparts to remove phloem sap from its host plants. Hundreds to thousands of SLF individuals can sometimes be found on a single tree. Surprisingly, even at these high numbers, death of hosts is only known to occur on grapes and a few sapling trees, although branch dieback on trees has occurred. Further research is needed to determine the longer-term impact of the stress of so many SLF feeding on trees has on secondary problems.

In addition to damage to hosts from feeding, SLF is also considered a nuisance pest. SLF excretes large quantities of honeydew which drops down onto leaves, branches, tree bark, driveways, cars, and anything else that might be underneath an infested host. The honeydew also has its associated black sooty mold, which makes it more unsightly. On sunny days the honeydew can be seen “raining” down from SLF infested trees.

Abundant honeydew-/sooty mold-covered foliage may reduce photosynthesis and further stress trees. In addition, many bees, wasps, and other insects that feed on sweets are attracted to the sugar rich honeydew. Because densities of SLF are so high, the honeydew/sooty mold can be quite significant and impactful to homeowners and growers.

An impressive breadth of hosts

An interesting aspect of SLF’s ecology is that it changes the plants it feeds on as nymphs and adults develop over the season.

table showing host plants preferred by spotted lanternfly nymphs and adults
This table is a (non-extensive) representation of common host plants that spotted lanternfly feed on during the season. The table allows knowing when to start monitoring for activity of nymphs and adults, and what host plants they are likely to be on. It is recommended to always monitor for SLF infestations, since densities change over time both within the season and between years even on the same host plant. Tree of heaven, Ailanthus altissima, is an invasive tree and a highly preferred host. Information in this table is based on observations in Eastern Pennsylvania and may vary based on local conditions. Image: https://extension.psu.edu/spotted-lanternfly-management-guide.

How can SLF be managed?

Managing SLF is challenging, as is the case for many emerging, invasive species. It is unlikely you can stop it from coming onto your landscape or farm, and unlikely you can get rid of all of them. Given this, the goal is to reduce SLF populations to acceptable levels. Using an Integrated Pest Management (IPM) approach will result in the greatest success.

At this time, natural enemies are not reducing SLF populations. However, many generalist predators (spiders, assassin bugs, birds, etc.) are feeding on SLF, a parasitoid brought into this country years ago for spongy (formerly gypsy) moth control has been found attacking SLF, and two fungal pathogens were also identified, one of which (Beauveria bassiana) is commercially available. Further research is underway to identify measures to enhance the impact of these biological controls for SLF.

Cultural controls can be implemented. This includes destroying the overwintering egg masses, putting traps (circle or sticky traps) on trees to catch the nymphs and adults as they move up trees, and removing tree of heaven. Numerous studies have examined the efficacy of contact and systemic insecticides against SLF (see websites below).

We need you!

Please assist in tracking SLF to help slow the spread of SLF and improve its management. If you find SLF, please report it to your State Department of Agriculture or University Extension Service. In Maryland, report SLF at the MDA website (click on “Report Spotted lanternfly here”).

For more information

By Dr. Paula Shrewsbury, Professor and Extension Specialist in Ornamental and Turf IPM in the Department of Entomology at the University of Maryland