Notes from Sophie's Summer Internship

Over this summer I was fortunate to have the opportunity to work with the Burghardt Lab here at the University of Maryland. My work focused on assisting Eva Perry, one of the lab’s master’s students, with insect collection across Baltimore, MD. The research aims to explore the relationship between tree management and insect populations. Being able to explore that relationship could lead to a better understanding of how insects choose what and where to populate.

Observing, Collecting, and Identifying Our City’s Insects

The most significant portion of my internship involved doing insect sampling throughout Baltimore. This involved vacuum sampling, looking for signs of insects on branches and leaves, and doing leaf assessments to compare mechanical and insect damage. I also helped to process and organize collected insects back in the lab by identification. From my time working on this project, I gained a more comprehensive understanding of insects. As an agricultural science major, the majority of my education had been largely plant science focused, with entomology on the backburner. It was insightful to have those roles reversed this summer.

Fig 1. Cranefly collected by vacuum sampling.

Checking in on Baltimore’s Young Street Trees

While I spent most of my summer collecting insects with Eva, I also participated in our Grand Challenges project to assess the health of Baltimore’s street trees. This involved measuring photosynthetic potential, tree diameter and height, inspecting the trees for insects or signs of their presence, and identifying any signs of disease or damage.

My participation in this project really taught me how to look for the tiny things and how to train my eyes to be able to spot even the smallest insect. This project also allowed me to put my education in plant science to work, as it came in handy to identify not only the trees themselves, but also diseases or other issues that affected the trees’ overall health.

Fig 2. Sophie and Maggie recording observations on a street tree in Baltimore, MD.

Wrapping Up a Buggy Summer

My time with the Burghardt lab this summer not only let me apply my knowledge I’ve learned as an undergraduate, but it also opened my eyes to a whole new world. I gained an even greater appreciation for insects, and I am now looking to pursue a career in entomology, due largely to my experience this summer. It wouldn’t be without the amazing help I had from everyone on the team and I’m so glad I will be continuing my work with them throughout this semester.

Fig 3. A milkweed tussock moth caterpillar found near a focal tree site.

Written by Sophie McCloskey, undergraduate student

Autumn Gold: Don’t let your leaf litter go to waste!

It’s about that time of year again- when cooler temperatures and shorter days signal that winter is coming, and our deciduous trees drop their leaves. For most residents, this also means hours of labor collecting the fallen leaves and piling them on the curb to be picked up along with other municipal waste. We have traditionally used the words “debris” and “litter” to describe dead plant material, indicating it is trash that should be bagged up and sent to the landfill. But this is certainly not the case! Dead leaves are a valuable resource, and the common practice of removing them from the home landscape has unintended environmental impacts.

The Natural cycle

Forested ecosystems have evolved with the annual input of fallen dead leaves. Here in Maryland, deciduous forests have been around for at least 10,000 years- since the last ice age! When trees drop their leaves in a forest, they are not wasted. Fallen leaves (and other organic materials like dead wood) nourish soil microbes and decomposers. They also add structural complexity (think air pockets) to the soil surface, which increases stormwater retention and provides habitat for innumerable small animals. Those small animals, including insects, feed on the litter, breaking it down into smaller pieces. Over time, fungi and other microbes completely transform the remnants of leaf litter into nutrients such as nitrogen that are recycled through the ecosystem year after year and carbon that can be sequestered belowground.

Figure 1: Removing leaves can negatively impact soil health and beneficial insect populations through many potential pathways. Illustration credit: Maggie Lin

Leaf Removal Impacts on Soil Health

Our lab has recently published research that humans may disrupt this important natural cycle when they rake (or blow) and remove fallen leaves from their yards each fall (Figure 1). This research compared areas of suburban Maryland yards where fallen leaves had been historically removed (such as in front yards) or retained (such as in back yards). In areas of Maryland yards where leaves were consistently removed each year, decomposition rates decreased by 17%, and soil carbon storage decreased by 24%. Removing leaves leads to poorer soil health!

Max Ferlauto (lead on the project) also performed an experiment: areas where leaves had been historically removed were retained and vice versa. Concerningly, two years of newly retained leaves was not enough to restore those soils' decomposition rates and carbon storage. This highlights that our yard management choices can have lasting impacts, and restoring ecosystem functions like decomposition and nutrient cycling in depleted soils may take time.

Leaf Removal Impacts on Insects and Other Animals

In contrast, insect communities seem to bounce back quickly when you start retaining leaves. While a few species of insects are pests, most insects benefit humans because they serve as pollinators, predators, decomposers, and food sources for birds and other wildlife. In the same way that providing flowers helps beneficial insects in the summer, providing shelter helps beneficial insects in the winter. The most common locations for overwintering insects are on the ground inside dead leaves or wood, underground in shallow chambers, or on twigs (Figure 2). Removing fallen leaves directly kills any insects sheltering inside the leaves, while any insects that remain near the soil surface may be exposed to more variable temperatures without the buffering effect of a leaf layer (Figure 1). Together these processes may result in smaller and/or less diverse insect communities. In fact, in the same yards where soil processes were measured, there were 40% fewer moths and butterflies emerging in the spring. Fewer moths and butterflies mean fewer caterpillars for birds, which rely on the spring insect bonanza to fuel successful migrating and breeding.

Figure 2: Examples of common overwintering locations for insects include tree holes, branches and twigs, in fallen leaves, and burrowed below the soil surface. Illustration credit: Maggie Lin

Landscaping Recommendations

Ironically, we may create even more work for ourselves when we remove fallen leaves because many processes that naturally occur on their own must now be actively managed. Fertilizer and mulch must be purchased and applied; soil must be aerated; stormwater runoff infrastructure must be maintained, etc. We spend a lot of time and money, yet ultimately degrade the quality of the environment for other plants and animals.

If you already manage an area for leaves, great! If you don’t, consider tweaking your landscape management this fall. Are there zones of your yard where removing all leaves is unnecessary? While it is often not feasible or desired to totally “leave the leaves” it is worthwhile to leave them where possible. To make things look tidier, you can rake fallen leaves from grass lawns into garden beds with borders (Figures 3 and 4) or mulch some of them to reduce the overall volume. However, you will be surprised at how much the leaves decrease in volume over the winter. This is one instance where doing less is certainly doing more- it’s easier for us and better for the environment!

Figure 3: Dead leaves can be used as an alternative to mulch in garden beds. Leaves provide nutrients and water retention for plantings, and new growth pushes up through the leaf layer in the spring. Image credit: Karin Burghardt

Figure 4: Another strategy is to create “canopy shadows” or “soft landings” underneath canopy trees. Creating borders with stones or logs keeps leaves where you want them and provides a cue of care to neighbors. Image credit: Karin Burghardt

For more information

Nesting & Overwintering Habitat For Pollinators & Other Beneficial Insects

Waiting on Spring Garden Cleanup to Support Beneficial Insects

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Written by Kelsey McGurrin, Maggie Lin, and Karin Burghardt

Branching Out: My Summer in Urban Forestry

Written by Anne-Lucie Pierre, Undergraduate student at The University of Massachusetts Amherst

This summer, I had the incredible opportunity to work as an intern with the Karin Burghardt Lab in College Park, Maryland. My work centered around the city of Baltimore as we analyzed street trees located in different neighborhoods. Neighborhoods in the city of Baltimore follow specific classification criteria as communities with higher populations of minorities were often redlined. Unfortunately, this discrimination can result in the lack of access to environmental benefits such as healthy trees. Assessing tree health in a variety of neighborhoods would help to highlight the effects of environmental discrimination.

Mapping Baltimore’s Trees

While I usually rely on Geographic Information Systems (GIS) to create maps, this internship challenged me to step out of my comfort zone and use R, a programming language, to map and analyze spatial data. Using R, I was able to dive deep into the world of data analysis and visualization. Mapping was a crucial tool in the research process as it allowed the team to visualize raw data.

Fig 1. Map depicting sampled Norway (green markers) and Red (orange markers) Maple trees throughout the city of Baltimore.

Assessing Tree Health

In addition to mapping, a significant portion of my internship involved assessing the health of trees. This meant getting up close and personal with Baltimore’s urban trees. I measured tree dimensions (DBH, height, etc.), conducted photosynthesis measurements, and scanned trees for signs of pests and diseases. A key threat I looked for was the infamous Spotted Lantern Fly.

Through these assessments, I gained a deeper understanding of the challenges urban trees face and the importance of monitoring tree health. This hands-on experience not only taught me the technical skills needed to evaluate tree health but also strengthened my understanding of management in urban ecosystems.

Fig 2. Kelsey and Anne measuring DBH on a street tree in Baltimore.

The Bigger Picture

My internship in Baltimore wasn’t just a learning experience––it was a chance to make a tangible impact on the city’s urban trees. Being able to collaborate with the team at the Burghardt Lab was an amazing experience that will forever play a huge role in all my future endeavors. From mapping points to performing health assessments, I enjoyed every bit of it. This experience has deepened my passion, furthering my excitement to continue exploring how technology can be harnessed to protect our natural resources. Thank you all!

Fig. 3 This southern red oak (Quercus falcata) was one of our more substantial tree finds along the streets of Baltimore during sampling.

Insects: Our Most Under-Appreciated Neighbors

Why should I want bugs, insects, and creepy crawlies in my yard or garden?

Insects are an incredibly diverse group of organisms, with 91,000 described species in the United States and likely an equal number yet to be described by scientists. Only an exceedingly small fraction of these species ever have negative impacts on humans as “pests” (<1% of species). Often the overabundance of pest species is due to human agricultural and landscape practice choices. The vast majority of insects in shared spaces with humans like yards and parks are going about their own lives. In addition to being fascinating creatures deserving of habitat in their own right, they also often contribute to unnoticed but very important tasks that help humans, termed “ecosystem services.” The next time you see one of these critters in your yard, consider thanking them rather than smashing them.

What are ecosystem services?

Ecosystem services are benefits that humans gain from the environment. Examples of ecosystem services include water filtration, raw material production, erosion control, and pollination. Some ecosystem services, like the maintenance of atmospheric gasses (e.g. plants remove carbon dioxide and produce oxygen that humans breathe), are noticeable and directly impact our everyday lives. On the other hand, services like decomposition may go unnoticed because they indirectly affect us. 

Insects (and their arthropod relatives like spiders and earthworms) play vital roles in many ecosystem services. This is often due to insects interacting with plants in some way, though insects also provide food for many other animals. Below are some examples of the ecosystem services that insects contribute to.

Water filtration

Filter-feeding insects positively affect water quality because they remove particles of dead organic material. Insects retain many of the nutrients they filter out of the water, thus reducing the likelihood of algal blooms, their associated toxins, and dissolved oxygen “dead zones.” This is crucial because clean water provides habitat for other plants and animals like fish and amphibians. It also means less effort is required to purify water for human use. 

Types of insects that improve water quality:

• Blackflies, mayflies, stoneflies, and caddisflies (Note: the underlined insect groups are not “true” flies in the taxonomic Order Diptera; they are part of other orders.) 

Other types of organisms that improve water quality:

• Mussels, crayfish, snails

More information:

Why Care About Aquatic Insects

[Click to view full video on Flickr] A blackfly larva attached to the side of a tank and filter feeding on particles that float by in the water. Credit: Donald Hines, CC BY 2.0 DEED

Biocontrol

Biocontrol is when natural enemies are used to suppress pests and reduce the amount of damage they cause. Natural enemies are insects that are antagonistic to pest insects. There are three types of natural enemies: predators, parasitoids, and pathogens. Preserving natural enemy populations is crucial to reducing our reliance on pesticides because when natural enemies are active, pest outbreaks are less likely to occur in the first place. Predators need food all year, so they also need alternate prey available in order to prevent pest outbreaks. Pesticides eliminate beneficial insects in addition to pests, so they should be used only as a last resort.

Fun fact: Fireflies spend much of the year as larval predators belowground, feeding on pests like grubs in turfgrass yards. If no prey is available in yards, then there will be no display of adult fireflies in the summer.

Types of insects used for biocontrol:

• Beetles, lacewings, wasps, and dragonflies

Other types of organisms used for biocontrol:

• Fungi, birds, amphibians, reptiles, and mammals

More information:

Approaches to the Biological Control of Insect Pests

An adult samurai wasp lays eggs in a mass of brown marmorated stink bug eggs. Credit: Chris Hedstrom, CC BY-SA 2.0 DEED

Seed dispersal

Seed dispersal is when seeds are moved away from the parent plant. Seeds are moved when insects knock them off while feeding or when insects collect and then move seeds to a new location. Seed dispersal is important because it reduces resource competition between the parent plant and offspring plants. It also makes germination and seedling survival more likely, especially in arid climates. 

Types of insect seed dispersers:

• Ants (most effective), beetles, wasps, thrips, and some moths

Other types of seed dispersers:

• Fruit-eating animals (frugivores), such as some monkeys, lizards, and bats

• Unwitting animal dispersers of sticky seeds like this

More information:

Seed Dispersal - The Australian Museum

The Conservation Physiology of Seed Dispersal

Two ants carrying a plant seed. Credit: Mark Chinnick, CC BY-NC-ND 2.0 DEED

Decomposition/Nutrient Cycling

Nutrient cycling and decomposition are two important processes that rely on one another. Nutrient cycling is when soil nutrients are taken up by plants, insects eat plants, and then those nutrients are reintroduced into the soil when dead insects and droppings are broken back down into nutrients via decomposition. Decomposer insects help clear dead animals and plants off the ground which would otherwise accumulate everywhere. They also help create soil texture and circulate nutrients back into the soil, which plant populations and productivity depend on.

Types of insect decomposers:

• Many beetles, springtails, termites, wood cockroaches, and some fly larvae (maggots)

Other types of decomposers:

• Fungi, earthworms, pillbugs, and millipedes

More information:

Decomposers

An adult bess beetle crawls across a log. Bess beetles are important decomposers and return nutrients to the soil. Credit: Kelsey McGurrin, used with permission.

Supporting Food Webs

Insects are a main source of protein and nutrition for many animals (and even some plants). They play a crucial role in transferring energy from plants to larger animals that eat insects like spiders, birds, frogs, fish, bats, foxes, opossums, and bears. This wide food base that they provide allows for functioning, stable ecosystems that are resilient to disruptions.

Fun fact: By weight, there are roughly 300 times more insects than humans on Earth.

There are so many animals that eat insects, but here are just a few examples:

• Terrestrial bird species, in particular, feed their babies almost exclusively with insects, and if there are fewer insects, baby birds are less successful at fledging from nests.

• Popular fish like salmon, bass, and trout eat insects, especially when they’re young

• Grizzly bears will eat tens of thousands of moths a day to prepare for hibernation

Northern Mockingbird adult feeding a praying mantis to a young bird. Credit: Becky Matsubara, CC BY 4.0 DEED

Pollination

Pollination is the transfer of pollen between flowers, resulting in flower fertilization and seed/fruit production. It is an unintentional consequence of pollinators going from flower to flower to feed themselves. Pollination is crucial for human survival, as 80% of plant-based foods and products rely on animal pollination. According to the USDA, pollinated crops are worth $18 billion in the US alone. Foods requiring pollination include apples, blueberries, chocolate, coffee, grapefruit, peaches, peppermint, sugarcane, tequila, and vanilla.

Fun fact: beetles were likely the first insect pollinators- starting 200 million years ago!

Types of insect pollinators:

• Bees, wasps, beetles, flies, ants, butterflies, and moths

Other types of pollinators:

• Birds and bats

More information:

Pollination Basics

What is Pollination?

Why is Pollination Important?

Pollinated Foods

Blueberry Digger Bee pollinating blueberry flowers. Credit: Judy Gallagher, CC BY 2.0 DEED

Written by Yasmine Helbling, Kelsey McGurrin, and Karin Burghardt

Ants & Peonies: A Garden Variety Mutualism

Sometimes people ask what my favorite flower is. To me, this is an impossible question because it depends on where I am, what time of year it is, whether I’m looking for color, edibility, scent, etc. However, if we’re judging based on the sheer number of photos I have taken of them, the winner is peonies.

Some of my many peony photos.

My grandma Duffy had a patch of peonies in her yard. No late spring visit was complete until we had walked outside to marvel at their huge pink blooms. The flowers were also quite fragrant, and I remember on more than one occasion sticking my face into the soft petals, inhaling, and getting an ant up my nostril. It’s a wonder my enthusiasm for entomology remained intact.

The house I am living in now also has peonies planted outside. The first year I saw them bloom, I went out to (carefully- I’ve learned my lesson) sniff the flowers and again saw ants crawling all over them. Suspecting that these ant sightings on peonies were more than pure coincidence, I started doing some research online. Turns out this is another fascinating example of a plant-insect interaction!

Peonies (genus Paeonia) are perennial herbaceous plants. According to The Old Farmer's Almanac, they can be very long-lived: even 100 years! They are native to Asia, Europe, and western North America, and scientists currently recognize 33 different species. Humans have cultivated the plants for culinary and medicinal purposes for thousands of years, though in the United States they are most common as ornamentals. 

Many people before me have noticed an association between peonies and ants. Unfortunately, some gardeners assume that the ants are harming their peonies and must be removed. This is not true! In reality, the peony plants have gone out of their way to recruit ants as bodyguards using extrafloral nectaries and we should leave them alone. Spraying insecticides is unnecessary and could harm more than just the ants.

Extrafloral nectaries are small spots on the underside of peony flowers (and many other plants) which secrete nutrient-rich sugars as a kind of lure for predatory insects like ants. 

Nectar droplet on a peony flower bud. Photo credit: M.J. Raupp

Once a scout ant stumbles upon a nectary, it sends out pheromone signals to the rest of its colony and together they set up patrols all around the plant. The ants essentially get a source of free food, and they are willing to defend their turf. Whenever other insects like thrips try to munch on the seemingly vulnerable peony flowers, ant bodyguards attack. By preventing damage to reproductive parts (flowers), ants help the plant set seeds and get its genes into the next generation. It’s a classic food-for-protection scheme, and since both parties benefit from interacting, biologists call this kind of relationship a mutualism.

You may have heard an old wives tale about peonies and ants: supposedly, the flowers won’t open unless the ants are there to “tickle” the buds. While this story is cute and may convince people to leave the ants on their peonies alone, it isn’t true. Peony flowers will open even without ants around. 

So what should you do if you want to make a bouquet of peonies without bringing ants into your house? If flowers are already open, hold them upside down and gently shake them to dislodge any ants hiding inside the petals. However, the easiest method is to cut flower buds off the plant BEFORE they fully open- when they’re still in the “marshmallow” stage. Wipe or rinse any ants off, then set the stems in a vase with water and the buds will fully open within a couple of days.

Flower buds in the “marshmallow” stage (shown above) will give slightly when pressed. Photo credit: F. D. Richards from Clinton, MI, CC BY-SA 2.0, via Wikimedia Commons

Written by Kelsey McGurrin

Remembering Summer (Caterpillar) Celebrities

The Mid-Atlantic winter season is now in full swing - at least, according to the calendar. This means the Burghardt lab is in the depths of data analysis for last summer’s projects. Seeing the results of our field season come together is very exciting, but it does make us sentimental for some of the fascinating Lepidoptera we found during data collection. While each caterpillar we find munching away on the tree leaves is something special, every so often a discovery is met with particular excitement (and a quick little photoshoot) from the samplers. The following are a few of the species that really captured our attention last summer.

Spun Glass Slug Moth

Scientific name: Isochaetes beutenmeulleri

Insect Family: Limacodidae

Host Plants: Normally beech and oak trees. We have found them on oaks (Quercus spp.) and sycamore (Platanus occidentalis)

Image description: Late instar I. beutenmuelleri, collected from SERC BiodiversiTREE field site, Aug 2022. Photo credit: Eva Perry & Kelsey McGurrin

Photos rarely do this caterpillar justice! Spun glass slug caterpillars are one of the more fantastical caterpillars that can be found in the Mid-Atlantic. As their common name suggests, these ethereally translucent caterpillars resemble remarkably delicate little pieces of spun glass, an appearance more akin to ocean-dwelling nudibranchs than to many other caterpillars found in eastern North America. This caterpillar’s range spans from southeastern New York to Florida, and as far west as Missouri, eating oak and beech tree leaves in deciduous woodland before shedding their protective tentacle-like lobes and building a cocoon. This species, like many other hairy or fuzzy caterpillars, falls firmly in the “look, but don’t touch” category – their lobes are covered in hundreds of tiny spines that pack a seriously painful and long-lasting sting!

Polyphemus Moth

Scientific name: Antheraea polyphemus

Insect Family: Saturniidae

Host plants: Many shrubs and trees. We have found them on oaks (Quercus spp.) and ironwood (Carpinus caroliniana)

Image description: Middle (top) and late (bottom left and right) instar A. polyphemus, collected from SERC BiodiversiTREE field site, summer 2022. Photo credit: Eva Perry & Karin Burghardt.

Named for the giant cyclops Odysseus encounters along the course of his decade-long voyage home, the Polyphemus moth caterpillar is a striking green behemoth that can reach a length of over seven centimeters in its final instar. The Polyphemus moth is found nearly everywhere on the North American continent excluding Nevada, Arizona, and the far north. This species eats the leaves of a variety of woody plants and trees, including ash, elm, and oak trees. A member of the giant silk moth family (Saturniidae), the Polyphemus caterpillar constructs a finely-spun cocoon within which to pupate, often in the leaf litter below its host tree. Like many other Lepidoptera species, Polyphemus moth caterpillars will sometimes “clip” the leaves they are eating. This means that once they have eaten the leaf, they will chew through the petiole, letting the leaf remnants drop to the ground, which may suppress plant defenses through chemicals in the caterpillar’s saliva (Dussourd 2022).

Question Mark Butterfly

Scientific name: Polygonia interrogationis

Insect Family: Nymphalidae

Host plants: Elm, hackberry, hops, and nettles. We have found them on elm (Ulmus americana)

Image description: P. interrogationis early (top) and late (bottom left and right) instars, collected from SERC BiodiversiTREE field site, summer 2022. Photo credit: Eva Perry & Kelsey McGurrin

One of the few species of butterfly we encounter on the trees we sample, the “question mark” caterpillar (named for wing patterns on the adults that look like question marks) can be found from southern Canada to central Mexico and Florida. These caterpillars’ spines can vary in color, most commonly orange and red, but can sometimes be yellow or black. Question mark caterpillars can most frequently be found eating elm, but sometimes will eat hackberry, hops, and nettles. We usually find them feeding in groups, especially as early instars. Unlike many of the species we find at BiodiversiTREE (which overwinter in their pupae), members of the Polygonia genus – including the question mark butterfly – overwinter as adults, some individuals even migrating southwards before winter.

Laurel Sphinx Moth

Scientific name: Sphinx kalmiae

Insect Family: Sphingidae

Host plants: Ash, fringe-tree, privet, and other plants in the olive family. We have found them on green ash (Fraxinus pennsylvanica)

Image description: Early (top left), middle (top right), and late (bottom) instar S. kalmiae, collected from SERC BiodiversiTREE field site, June 2022. Photo credit: Eva Perry & Kelsey McGurrin

Despite its common name, the Laurel sphinx moth caterpillar can most frequently be found on plants in the olive family (Oleaceae), such as lilac and ash, across eastern and central North America. Their most striking feature is perhaps its blue and black horn on the eighth abdominal segment – the horn is a common feature among many hawkmoth caterpillars (often aptly called “hornworms”), but this color and patterning is unique to the Laurel sphinx. When we first found this particular individual, it was only a couple of centimeters long and had no unique markings. Several species of sphinx caterpillars can feed on ash trees, so in order to identify it we reared it in the lab until distinguishable features developed. Laurel sphinx caterpillars can grow to an impressive length of eight centimeters before spinning their cocoons and pupating.

Greater Oak Dagger Moth

Scientific name: Acronicta lobeliae

Insect Family: Noctuidae (subfamily Acronictinae)

Host plants: Oaks (Quercus spp.)

Image description: Early (top left), middle (bottom left), and late (right) instar A. lobeliae, collected from SERC BiodiversiTREE field site, summer 2022. Photo credit: Kelsey McGurrin

This fuzzy little oak specialist can be found in woodlands and forests of North America’s eastern coast, from Canada to Florida. The greater oak dagger moth is of some interest because of its two distinct regional larval color schemes. In Maryland, the caterpillars closely resemble the image above: light gray with a creamy white dorsal stripe, and deep red patches on the top of the head surrounded by gray speckling. This contrasts with caterpillars of what is presumed to be the same species further north, whose coloring is much darker and lacks the red patches on the head capsule. The position of the hairs on the greater oak dagger moth’s caterpillar make for excellent camouflage on bark and branches, giving the caterpillar a flattened appearance that is difficult to distinguish from its background. This was another caterpillar that we needed to rear in order to identify it to species. There are approximately 40 species of Acronicta in our area, many of which feed on oak, and (as mentioned above) their appearances as caterpillars can vary a lot. Thankfully this one survived in lab long enough to develop some distinguishing features!

Sources

Beadle D & Leckie S, 2012. Peterson field guide to moths of Northeastern North America. Houghton Mifflin Harcourt, New York, New York, USA.

Dussourd D, 2022. Salivary surprise: Symmerista caterpillars anoint petioles with red saliva after clipping leaves. PLoS ONE 17(3): e0265490. DOI: 10.1371/journal.pone.0265490.

Wagner DL, 2005. Caterpillars of Eastern North America: A Guide to identification and natural history. Princeton University Press, Princeton, New Jersey, USA.

Written by Eva Perry and Kelsey McGurrin

Maryland's 5 Million Trees Project

¿Hablas español? Una traducción de esta publicación se puede encontrar aquí

Community members planting trees. Photo credit: Alex Indigo, CC BY 3.0 DEED

What is an Urban Heat Island?

Cities are really, really hot! Picture this: you are walking across a parking lot downtown in the summer. The sun is out, there is barely a breeze, and you are feeling the heat. That heat isn’t just from the sun! It radiates from all the concrete of the roads, sidewalks, and buildings around you. Then, you see a park with large canopy trees shading the walkway; maybe walking through it will provide some relief. As you enter the park, you can feel cooler temperatures wash over you - more than just from escaping the sun. In fact, trees can lower air temperatures underneath their canopy by 20–45°F through shading and an additional 2–9°F by moving water up through their roots and releasing it through their leaves through a process called evapotranspiration. This can make a big difference in cities, which experience higher temperatures because of all the concrete and asphalt surfaces. These hotter temperatures in cities are part of what is called the urban heat island effect, and it can cause adverse health impacts for residents. Trees are one answer to this problem. 

Street and median strip trees growing in downtown Baltimore, Maryland. These trees provide cooling benefits! Photo: K. Burghardt

Trees in cities also do other essential things for residents. They take up stormwater to reduce flooding, prevent erosion, and improve residents' mental health and well-being. They can provide habitat for birds and pollinators! Read more about the benefits of planting trees and considerations for climate change here.

Unfortunately, tree cover is rarely equally distributed across city neighborhoods. Many places within Maryland cities need more trees to approach the canopy cover goal of 30-40% cover, which will provide maximum cooling benefits.

The urban trees grant program

The Maryland General Assembly passed historic legislation HB 991 during its 2021 session.

The bill establishes that it is the policy of the State to support and encourage public and private tree-planting efforts, with the goal of planting and helping to maintain 5 million sustainable native trees in the State by the end of calendar 2031

It also stipulates that at least 500,000 of those trees be planted in an “underserved area,” defined as an urban area as delineated by the US Census Bureau that also meets one or more of the following criteria:

1. Historic disenfranchisement: A neighborhood that was, at any point in time, redlined or graded as “hazardous” by the Home Owners’ Loan Corporation; OR

2. Unemployment: A census tract with an average rate of unemployment for the most recent 24-month period for which data are available that exceeds the average rate of unemployment for the state; OR

3. Household income: A census tract with a median household income for the most recent 24-month period for which data are available that is equal to or less than 75% of the median household income for the state of Maryland during that period; OR

4. Housing project: A housing project as defined in Section 12-101 of the Housing and Community Development Article.

The Chesapeake Bay Trust (those “Save the Bay” license plate folks) runs the grant program for the State of Maryland. You can find the request for proposals (pdf) and explore the portal to apply here. Applications can be for planting and maintaining any number of trees from 25 to 6,000. Community groups, churches, and non-profit organizations are all eligible to apply.

This is a fantastic opportunity if you have a corner, vacant lot, park, church, community space, or even private property where adding trees would enhance the neighborhood for all!

Is my community eligible to apply?

The state has put together a handy interactive map where you can search your address and see if your community qualifies for the program. We’ve added a screenshot from the site below, but you can zoom into your neighborhood from the website. 

The orange neighborhoods above are the urban areas in Maryland eligible to apply for money to plant trees through the Urban Trees Grant Program. Photo credit: Maryland DNR

How do I know what trees to plant?

Chesapeake Bay Trust provides substantial guidance on its website. One key idea is that when you choose the trees you want to plant, try to choose many different tree species for your neighborhood rather than just choosing one. By choosing a variety of tree species, you are following the diversification principle of Integrated Pest Management (IPM), which means it is less likely that the entire tree canopy will be damaged or killed when a pest or disease inevitably arrives. In other words, you will still have a tree canopy that benefits residents! This is becoming increasingly important as cities lose trees to introduced pests like the Emerald Ash borer, which has been attacking and killing ash trees all over the eastern half of the United States. Communities that planted all ash trees in the past now have more significant expenses - and many trees to replant.

To make selecting tree species easier, our lab, working on behalf of the University of Maryland Extension (UME), put together an interactive list of eligible Maryland native tree species for planters. These species are known to do well in various challenging urban conditions, and there is a lot of information to allow you to put the right tree in the right place. You can choose trees based on fall leaf color, flowers, habitat for pollinators, edibility for humans, and more! We can’t wait to see what you pick!

Screenshot of a downloadable interactive tree species selector tool for choosing trees to plant in urban areas of Maryland.

Download the full list here

Written by: Karin Burghardt, Kelsey McGurrin, Elizabeth Butz, and Eva Perry

Eastern Branch EntSoc 2022

After a couple of pandemic years, our lab was finally able to attend an in-person conference together! Here we are at the Bellevue Hotel in downtown Philadelphia:

Research Presentations

“Urbanization and Insect Life Cycles: Challenges and Opportunities for Non-Pest Insects.” Lauren Schmitt and Karin Burghardt, University of Maryland, College Park, MD

“Assessing the Impacts of Leaf Litter Management on Overwintering insects in Urban and Rural Areas.” Max Ferlauto1, John Parker2 and Karin Burghardt1, 1University of Maryland, College Park, MD, 2Smithsonian Environmental Research Center, Edgewater, MD

“Tree species diversity influences periodical cicada oviposition.” Kristin Jayd1, Zoe Getman-Pickering2, John Lill3, Martha Weiss4, John Parker5 and Karin Burghardt1, 1University of Maryland, College Park, MD, 2George Washington University, Washington, DC, 3The George Washington University, Washington, DC, 4Georgetown University, Washington, DC, 5Smithsonian Environmental Research Center, Edgewater, MD

“Impacts of seed coat treatments on insect damage and natural enemy community composition.” Brendan Randall1, Kim Komatsu2, John Parker2, Kelsey McGurrin1, Sarah Alley2 and Karin Burghardt1,2, 1University of Maryland, College Park, MD, 2Smithsonian Environmental Research Center, Edgewater, MD

Caterpillar recruitment in response to tree diversity in an experimental forest. Kelsey McGurrin1, John Parker2 and Karin Burghardt1,2, 1University of Maryland, College Park, MD, 2Smithsonian Environmental Research Center, Edgewater, MD

Tree species diversity and architecture determine spider abundance in a forest diversity experiment. Elizabeth Butz1, Lauren Schmitt1, John Parker2 and Karin Burghardt1,2, 1University of Maryland, College Park, MD, 2Smithsonian Environmental Research Center, Edgewater, MD

Awards

Excellence in Early Career Award: Karin

2nd place in Master’s student talks: Brendan

Entomology Games champions: UMD Checkerspots (including team member Brendan!)

DC's famous cherry trees, part 2: Variation in the trees and varied threats to their health

In our first post we highlighted the historical role of the famous cherry trees in enacting plant inspections and the role of integrated pest management in keeping the cherry trees healthy. There is much more to the cherry trees than the pests they may have arrived with in 1912 and the insects that could threaten them in modern times. In this blog we explore the variety of trees that are included among the famous cherry trees and discuss some of the non-pest threats to their continued well-being. 

Where are the cherries on these cherry trees? 

Visitors to the cherry trees, especially young visitors, may be disappointed to learn that grocery store cherries do not come from these cherry trees. The trees that grow grocery store cherries are in the same genus as the famous trees along the National Mall. A genus is a scientific categorization that groups related species. Cherries are in the Prunus genus, which also includes other stone-fruit, like plums, apricots and even almonds!

Figure 1: A collage of cherry blossoms, some of which can be found in Washington DC. Cherry varieties can differ in flower color, size and shape. Credits (clockwise from top): Silverije, CC BY-SA 3.0, John Bauld from Toronto, Canada, CC BY 2.0 via Wikimedia Commons; Kelsey McGurrin

Astute visitors might also notice the variation in bloom color – from white to deep magenta. The cherry trees along the National Mall aren’t a single species, but are made up of 11 varieties of cherries, which encompasses both different species and different cultivars within species. 

The cherry trees in Washington DC were famously a gift from the Japanese government – and the specific species and varieties are native to Japan. However, there are Prunus species that are native to the United States. The American plum (Prunus americana) and the chokecherry (Prunus virginiana) are two examples that can produce similarly beautiful blooms. However, before you plant Prunus species in your yard, be forewarned that both native and non-native Prunus species can be quite high maintenance – with lots of disease and pest concerns. 

Cherry trees don’t swim

In the first blog we learned integrated pest management is used to keep the cherry trees pest free – but pests are just one of the threats that Washington DC’s cherry trees are facing. Soil compaction from so many visitors, climate change and rising sea levels are also pressing issues. The most famous of the DC cherry trees border the Tidal Basin where, as the name suggests, the tides from the Potomac River rise and fall twice a day. Tides are rising as part of global climate change, threatening the infrastructure of the Tidal Basin and the cherry trees that surround it. For the past several years the National Park Service has been forced to close parts of the sidewalk that encircle the Tidal Basin because they are partially or entirely submerged. 

Figure 2: The Tidal Basin in DC floods regularly. Cherry trees are visible in the left background with their roots at or near the waterline. Credit: G. Edward Johnson, CC BY 4.0, via Wikimedia Commons

Cherry trees are not well-adapted to aquatic environments, so any flooding would weaken their health, but the situation is made worse because of the type of water that floods the Tidal Basin. The Potomac River is connected to the partially salty or “brackish” Chesapeake Bay. Thus, rising tides can also mean an influx of salty water, which weakens the cherry trees even more than fresh water might. Mitigating climate change and thus, stopping tides from rising further, would be the most complete solution to help the cherry trees – but that requires near global cooperation. Shorter term solutions are also being considered, including re-engineering the sea-wall that fortifies that Tidal Basin. The sea wall was built in 1882 and has not been substantially modified since! 

Climate change and cherry blooms 

Peak bloom, defined as the time when 70% of the flowers on the cherry trees are open, changes every year. This year, in 2022, the National Cherry Blossom Festival is scheduled from March 20 - April 17, but peak bloom has happened as early as March 15th in 1990 and as late as April 18th in 1958. (You can keep track of the progress on the bloom with the National Park Service’s Bloom Watch!).

Figure 3: Stages of blooming from a green bud to puffy blossoms. The timing of each stage is carefully tracked each year. Credit: NPS

With climate change, the time of peak bloom will be more variable and the bloom will become less synchronous. This could be a problem for the plants if they bloom during warm spells and winter weather returns. If there is a frost after the cherry buds are in the process of blooming, it can kill the buds, and the trees do not have the resources stored to put out buds for a second time in one year. This happened in 2017, killing half the buds before they could bloom. Changing temperatures can also be harmful for insects and other animals that rely on the trees. 

Cherry trees in the next century

The cherry trees face many challenges, but they also have many advocates. Their health is monitored closely by many agencies and problems are treated as they arise. Design firms are re-imagining how the Tidal Basin and the low-lying National Mall can survive higher sea levels. Horticulturalists and breeders are working on creating varieties of Prunus trees that are more resistant to climate extremes, diseases and pests. Through these careful efforts, the cherry trees will hopefully be around for centuries to come.

By Lauren Schmitt, Kelsey McGurrin, and Karin Burghardt

DC’s famous cherry trees, part 1: A case study for IPM

¿Hablas español? Una traducción de esta publicación se puede encontrar aquí

Every year more than a million people flock to Washington, DC to see the cherry blossom trees in full bloom around the Tidal Basin. The cherry trees, which were a gift from the Japanese government in 1912, have long been a draw for tourists and locals. Today there are 11 types of non-native flowering cherry trees on the National Mall. 

Figure 1. Cherry trees in bloom around the Tidal Basin in Washington, DC. The National Cherry Blossom Festival attracts an estimated 1.5 million visitors a year! Photo: Matthew G. Bisanz, CC BY-SA 3.0, via Wikimedia Commons

While the famous cherry trees were planted in 1912, they weren’t the first cherry trees that arrived from Japan. The first shipment arrived in 1909, but was burned on the grounds of the Washington Monument after the trees were found to be infested with many kinds of non-native pests including scale, thrips, and moths. (Though, a few trees from the 1909 shipment may have been saved for study by entomologists!) The inspection and subsequent destruction of the trees was controversial not only for its dramatic outcome, but because at the time the United States Department of Agriculture (USDA) was not authorized to inspect private introductions of plants into the country. These circumstances led Congress to pass the Plant Quarantine Act of 1912, the precursor to today’s Animal Plant Health Inspection Service (APHIS). The goal was to prevent harmful organisms from being accidentally introduced into the United States via inspections, quarantines, and continued monitoring. Those same practices are also our best defense against pests on a more local level.

Keeping the cherry trees healthy

Today the health of the Tidal Basin cherry trees is still closely monitored by National Park Service officials. The foundation of their approach is integrated pest management (IPM). IPM is a sustainable strategy for managing insects based on monitoring trees during the times of year that potential pests are most likely to be a problem. If a pest outbreak that could harm the tree is detected, then multiple complementary tactics are used to keep pests numbers below thresholds that cause substantial harm. If you visited the cherry trees, you could likely find many insects and fungi, but few will be in numbers that would kill a tree – which is the ideal outcome of IPM!

Figure 2. Integrated pest management combines continued monitoring, evaluation, prevention and action to manage insect populations with lower costs and minimal impact on people and the environment. Image: Entomological Society of America

Local populations in a global world 

The official shipments of cherry trees from Japan to Washington DC are only a tiny, miniscule fraction of the movement of plants and animals around the globe. While some introductions are accidental, many organisms are moved purposefully, for agriculture or landscaping purposes. Up to 50-70% of non-native species arrived in their new regions with the horticultural trade! 

The prevalence of non-native plants is important because native insects might not be able to use the non-native plant species in the same ways, but also because non-native insects can move with the non-native plants, as seen in the doomed 1909 shipment of cherry trees. Monitoring and preventing new pests from establishing on trees native to the eastern US is the most powerful IPM strategy. Once a non-native insect establishes in a new area, it becomes harder to control their populations with IPM, meaning outbreaks can be more likely. The cherry trees are a beautiful and beloved addition to the Washington DC landscape, but they are also a cautionary tale of the effort required to safely add and maintain a plant species in a new environment. 

Tracking the blooms this spring

If you want to keep track of the predicted peak bloom time this year check for the National Park Service peak bloom forecast anytime after March 1st and for up-to-date live views check out the #Bloomcam of the tidal basin. If you would prefer a less crowded place to see cherry trees in bloom, the National Arboretum also has a collection of over 70 varieties of cherry trees that bloom all spring long. Keep your eye out for interesting native insects that eat the leaves or pollinate these trees!

Figure 3. Cherry blossoms in full bloom. There are 11 types of cherry trees on the Washington DC National Mall, ranging in color from white to deep pink. Photo: NPSPhoto

Further reading

• Cherry Blossoms, Insects, and Inspections, by Kelly Buchanan, Library of Congress

  • https://blogs.loc.gov/law/2012/03/cherry-blossoms-insects-and-inspections/

• Celebrating 100 Years of Washington, DC’s Cherry Blossoms, by Alyn Keil, USDA

  • https://www.usda.gov/media/blog/2012/04/04/celebrating-100-years-washington-dcs-cherry-blossoms

• National Park Service

  • https://www.nps.gov/subjects/cherryblossom/about.htm
    

Part 2 of this story is out now! Read it here.

By Lauren Schmitt, Kelsey McGurrin, and Karin Burghardt

Moths Have Ears (and Other Wondrous Facts)

I recently listened to a talk which I found particularly delightful. Dr. Akito Kawahara from the University of Florida was giving a virtual presentation to the Entomological Society of Washington. He highlighted his research into how moths use sound to defend themselves against bats, and along the way, he also reminded me that insects and plants were interacting with each other LONG before humans were a twinkle in the eye of the cosmos.

Here’s a summary of the facts which I felt were most awe-inspiring:

Moths Have Ears

The evolution of hearing in moths is one topic explored by Akito’s research. The original hypothesis was that moths had evolved hearing in response to pressure from their major predators, bats, who use sound to hunt. However, Akito’s group used fossils and genetic analysis to show that moth ears had actually evolved long before bats did. 

Giant leopard moth with wings removed to show ears. Photo credit: Donald W. Hall

Moths Can Scream

In order to jam the sonar signals which allow bats to track prey, moths can make noises of their own. For example, hawk moths can stridulate their genitals extremely quickly and essentially create a wall of ultrasonic noise that confuses any bats hunting them. Tiger moths use a membrane on their thorax to create clicks, and some toxic moths also advertise their distastefulness with specific sounds.

Details of the sound (a) and genital structures (b-d) that hawkmoths use to deter predatory bats. Figure credit: Barber and Kawahara

Moths Create Illusions

Some moths prefer to disappear when bats are chasing them. Giant silk moths have long “tails” on their wings which spin like fans behind them as they fly, scattering sonar signals. These make it hard for bats to tell exactly where they are, and an incorrectly-aimed attack is less likely to be lethal. If you’ve ever tried to produce quality audio for a concert or podcast, you know that soft surfaces absorb sound. Moths use this principle to their advantage and grow soft “fur” all over their bodies. By absorbing any incoming sonar, less signal makes it back to the bat, making it seem like the moth isn’t there at all. 

This video by Boise State researchers shows a bat aiming at the long "tails" of an African moon moth, then a luna moth. The bat manages to rip the tails off, but the moths, which can fly without them, skirt away to safety. Video credit: Jesse Barber Lab.

Moths are older than dinosaurs

The latest estimate puts moths at 300 million years old. In case you’re counting, this means moths were flying around for 50 million years before dinosaurs showed up. Even more bizarrely, the earliest moths had chewing mouthparts. A nectar-sucking proboscis (which is the standard now) wouldn’t have done moths any good before flowering plants existed! Butterflies, which are a subset of moths, appeared on the scene relatively recently, around 100 million years ago. They are primarily active during the day, which is another tactic for avoiding hungry bats.

A sphinx moth unfurls its proboscis to drink nectar from a flower. Photo credit: IronChris, CC BY-SA 3.0, via Wikimedia Commons

what about Moths in human-dominated landscapes?

Earlier this year, our lab published a review on how urbanization might change insect behaviors. Research has shown that human use of artificial light at night impacts many animals, including moths. Considering how critical sound is to their anti-predator defensive behaviors, moths are likely impacted by human-created noise as well. Until we know for sure, it is recommended that we all do our best to limit light and sound pollution at night. Akito published an article titled “Eight simple actions that individuals can take to save insects from global declines” which is definitely worth a read if you care about protecting our wondrous moths.

---

Kelsey McGurrin, lab manager

P.S. the Burghardt lab space at UMD was previously occupied by Dr. Charlie Mitter, Akito’s PhD advisor. Small world! (For humans, at least. We’ve been on earth less than half a million years.)

Suburban Lawn Study Launched

This research project studies the effects of leaving autumn leaf litter instead of removing it.

The Environmental Protection Agency (EPA) estimates that the United States generates about 35 million tons of yard waste each year. That is just a little less than the amount of municipal plastic waste! A large portion of yard waste includes leaf litter that is bagged or raked to the side of the street. But, leaf litter could be an important habitat for hibernating insects or for conserving the nutrients in the soil. So, our research is studying how leaving leaf litter in suburban lawns affects insects and soil decomposition.

Photo credits: Max Ferlauto

Our study uses emergence traps: small tents capped with two collection bottles. When insects wake up in the spring, they fly up to the highest and brightest thing they can find-- in this case the bottle at the top of the trap. They get tired flying around that bottle and drop into the bottom bottle, which is filled with a preservative fluid. Every couple weeks the bottom bottle is collected and replaced. We place two traps next to each other- one on an area where leaves are removed, and one where leaves are retained.

We also are studying soil decomposition using green and red tea bags. We weigh them, bury them, and after a certain amount of time, dig them up and re-weigh them. This allows us to calculate the rate of decomposition in areas where litter is retained or removed. This experiment is similar to studies taking place all across the world: http://www.teatime4science.org/

By Max Ferlauto

Raining Cats and Wasps

My car is parked beneath a big catalpa tree. I loved my parking spot this summer because it was always shady, which prevented my car from becoming an oven midday. Now in the last week, I’ve noticed another perk of my parking spot: it provides me with a front row seat to one of nature’s annual dramas.

There are two species of catalpa (sometimes spelled catawba) trees native to the southeast United States, though they are also cultivated outside of their native range because they grow quickly and have showy flowers. They are easily distinguished by their long seed pods, which look a lot like string beans. Another delightful feature of catalpas is that they have very broad leaves, which are perfect for hiding behind.

Man hiding behind a catalpa leaf near Antietam National Battlefield. Photo credit: K. McGurrin

One day last week I was getting into my car and noticed a big yellow and black caterpillar on the windshield. It had a “horn” on its abdomen, indicating it belonged to the Family Sphingidae, and knowing that it had likely been feeding on the catalpa tree overhead led me to identify it as a Catalpa Sphinx, Ceratomia catalpae.

Late instar Catalpa Sphinx caterpillar. Photo credit: Judy Gallagher, CC BY 2.0, via Wikimedia Commons

Finding one beautiful caterpillar on my car was nice, but then each time I revisited it over the next several days I was finding more and more fallen caterpillars. Some were on the ground beside my car, one got wedged into the trunk hinge, a couple more were on the hood… it was a downpour.

In the course of doing research, our lab ends up saying and writing “caterpillars” a LOT- often enough that we feel the need to shorten the original four syllable word to “cats.” So at my house this week, it has been raining cats.

As you may have deduced from the title of this blog post, it has also been raining wasps at my house. As apocalyptic as that sounds, the wasps raining down here are tiny and harmless to humans. In fact, I never even saw the wasps themselves. Instead, the indicator of their presence was the abundance of white cocoons found on every fallen caterpillar.

While all wasps are important predators, parasitoid wasps are sneaky about their work. Adults will lay eggs in or on caterpillars, and for a while the caterpillars will continue functioning as normal. Then the wasp egg will hatch and gradually eat away at its caterpillar host, ultimately killing it (this is the difference between a parasite and a parasitoid). In this way, parasitoids are a form of biological control which prevent populations of caterpillars from becoming so large that they inflict serious damage to plants.

If you’d like to see more awesome/gruesome details on caterpillar parasitism, check out this video from the Caterpillar Lab:

In the case of my catalpa tree and Catalpa Sphinx caterpillars, the identity of the parasitoid wasp is most likely Cotesia congregate. Pupae are the wasp’s most visible life stage, as many of them are often clustered together on top of a caterpillar. This was exactly the part of the drama which I was witnessing under my catalpa tree. A subset (according to our preliminary data from BiodiversiTREE, around 6%) of the caterpillar population overhead had been parasitized by wasps, died, and slid off onto my parking spot below. By the time I found them, many of the wasp pupae had already hatched and the new generation of adults had flown off.   

Three wasp pupae on the back of a Catalpa Sphinx caterpillar. All three are open at the top, meaning that the wasp has already emerged and flown away. Photo credit: K. McGurrin

Unfortunately, I can’t see the remaining (healthy) caterpillars from the ground. By looking carefully at the shape of the leaves overhead, I can see one branch with quite a bit of feeding damage.

Red circle highlights one area of the tree above my car with quite a bit of leaf tissue missing. This is likely from the feeding of many caterpillars. Photo credit: K. McGurrin

My guess is that the remaining caterpillars will soon finish eating in the treetops and crawl down the trunk to overwinter as pupae in the soil. Hopefully next summer I’ll have an encore performance of this drama, with each actor in their supporting ecological roles.

Written by Kelsey McGurrin, lab manager

Lab Members Presented At ESA

In very exciting news, the first presentations from (non-eponymous) Burghardt lab members hit the wide world in August at the Ecological Society for America National meeting. Max and Kelsey produced posters showcasing work within the BiodiversiTREE and BeanDIP projects respectively. We are very proud of the progress they are making. Check out their work below!

Assessing the impacts of seasonal leaf litter disturbance on overwintering pollinators and natural enemies
Max H. Ferlauto1 and Karin T. Burghardt1,2, (1)Entomology, University of Maryland, College Park, MD, (2)Smithsonian Environmental Research Center, Edgewater, MD

Seed coat impacts on soybean plant trait expression and fitness
Kelsey McGurrin1, Kimberly Komatsu2, John D. Parker2 and Karin T. Burghardt 1,2, (1)Entomology, University of Maryland, College Park, MD, (2)Smithsonian Environmental Research Center, Edgewater, MD

The Wonderful World of Soybeans

If you’d asked me about soybeans a year ago, I would probably think up images of the tofu and soymilk in my fridge. Little did I know then that I would be working on a project over the summer and would learn much more about soybeans than I ever thought I could know.

This past summer, I planted almost 600 soybean seeds in an experimental garden at the Smithsonian Environmental Research Center (SERC).

The soybean experimental garden in raised beds at SERC.

In addition to learning that soybeans are very resilient, surviving harsh rains and dry sunny days without water, I also learned how soybeans impact our daily lives – even if you don’t drink soymilk. Soybeans are much more than meat and milk replacers; they are actually the largest source of animal feed and the second largest source of vegetable oil in the world. And as I drove home from SERC at the end of that summer, I found that I recognized the small green leafy plants in almost all the fields I drove by – they were all soybeans! To my surprise, I discovered that the United States is the leading producer of soybeans and the second largest soybean exporter in the world, making it an important crop for the US economy.

Because soybeans are such an important crop for the US, many researchers are looking at ways to increase the productivity of soybeans. Although they are the same species, there are many varieties of soybeans made by different seed companies, bred and genetically modified for certain traits. Some soybeans can survive in very little water, some are resistant to fungi, and some are less palatable to insects. Farmers can potentially use this diversity of soybeans to increase their soybean yield.

Soybeans are often planted in monocultures of one variety, but if something like an insect or fungal disease comes through, and the variety is not resistant to this, a farmer will lose their entire soybean crop. Planting in polycultures, with more than one variety, could remedy this issue. In addition, studies have shown that increasing species diversity increases yield while preserving the same nutrient quality in agricultural hay fields and increases ecosystem productivity in grasslands. In our soybean garden, we planted four different varieties to see how they interacted in a polyculture.

We planted the varieties in a 6-plant arrangement so that all the plants could interact. We planted monocultures as 6 plants of the same variety, 2-variety polycultures with 3 plants of each variety, and 3-variety polycultures with 2 plants of each variety. We used all possible combinations, and with treatment replicates there were 588 plants total.

A group of 6 plants comprises one treatment combination. These combinations were either all 1 soy variety, 2 different soy varieties, or 3 different soy varieties.

After planting the soybeans, we measured several factors, including growth stage, height, percent herbivory, aspects of photosynthesis, and other traits. We took measurements on a tool called the Photosynq Multispeq, which measures a variety of photosynthesis variables, including relative chlorophyll, leaf thickness, and the efficiency of the leaf’s photosynthesis. For the traits, we harvested a sample of the leaves from the garden and measured their area, wet and dry mass, toughness, thickness, and used a pressure chamber on them to see if they were water-stressed. We also counted trichomes, which are tiny hairs on the leaf that you can see under a microscope. Even though we have to look at them under a microscope, these hairs are quite large compared to a small insect, so they are likely important in protecting leaves from insect herbivory.

Taking photosynthesis measurements on the soybean plants using the Photosynq tool.

In the fall, we harvested the soybeans and counted and weighed their beans. This was one of the most important measurements, because soybeans are annual plants, and what we consider “beans” are actually seeds which plants pass on to the next generation. Seeds are one of the best measures of a plant’s fitness. We then analyzed the data to answer the question as to how diversity affects productivity of the soybean varieties. Shown below are some preliminary results, and more results and statistical analyses are pending.

First, we found that the number of healthy beans produced per plant likely varies more between varieties than between different levels of diversity.

Healthy Beans

Varieties 31, 32, 67, and 83 with their average healthy bean number per individual plant in monoculture, 2-variety combinations and 3-variety combinations. Varieties 31 and 32 seemed to do better overall, with no clear trend between bean count and diversity.

The bean mass per plant includes all beans, healthy or unhealthy, and also showed more between-variety variation than variation within diversity treatments.

Bean Weight

The average bean mass per plant for each variety (31, 32, 67, 83) in monoculture, 2-variety, and 3-variety polycultures. Variety 67 once again did worse while the other plants produced a greater mass of beans.

In analyzing one of the measured traits, we found that the number of trichomes on a small circle taken from a leaf increased as diversity increased, although this may not be a significant difference.

Trichome Count

This graph again shows the Varieties 31, 32, 67, and 83. Only the monoculture and 3-variety polycultures were measured for trichomes.

Given that trichomes may act as herbivore repellant for plants, soybean plants in polyculture might be more resistant to herbivores. Results show that percent damage from herbivory in Varieties 31, 67, and 83 decreased from monoculture to 3-variety polyculture, although damage increased in the 2-variety polyculture in Variety 83.

Insect Damage

Average percent damage on the 2nd highest leaf on the plant, for all varieties in all diversity treatments.

Although we did not see soybean yield increase strongly with diversity, other beneficial traits such as protective trichomes may increase with diversity. This could protect plants from a potential pest outbreak when planted in polycultures. By continuing to analyze these factors, we will be able to see whether planting soybeans with greater varietal diversity may be beneficial. If diversity increases growth and yield, we may even be able to produce more soybeans with less land and increase our food productivity.

Written by Zoe Read, (recently graduated!) undergraduate student

My Year Playing with Litter

What does a bee know of a pandemic? Nothing; it does not understand its own species’ hardships nor ours. I watch as a blissfully ignorant bee flies by. Varroa mites, neonicotinoids, Colony Collapse Disorder—it's a lot to deal with. Yet this little bee has survived and keeps buzzing along. This gives me hope for our own COVID-19 crisis. I think that is okay. Right now it can be easy to be lost in despair. While we shouldn't become careless or take our privilege for granted, sometimes it is healthy to feel optimistic.

This is also how I feel about ecology. Too often we focus on our failings. In conservation, there are many. But it's hard to create change with sorrow clouding the mind. This is why I choose to study ways that each one of us (scientist or not) can help conserve our environment. 

My research investigates how homeowners can protect insect populations on their property by leaving leaf litter on their yards each autumn. Each year we remove more than eight million tons of leaf litter from residential homes. However, many insects, such as butterflies and moths carry out important parts of their life cycle in the leaf litter during the winter. Leaf litter also offers complex structures to hide in and protection from rapid temperature changes. As such, our autumn yard maintenance may either directly kill or make habitat unsuitable for many insects. The extent to which we are harming insect communities with these practices is unknown. We also don’t know if there are strategies, such as maintaining native diversity in our yards, that could mitigate the effects of this disturbance. Therefore, I’m studying how disturbing leaf litter, through adding, raking, or mulching leaves, affects insects that emerge from the forest floor each spring. I’m also examining if insect communities in diverse forests are more resilient to disturbance. 

Conceptual model proposing the effects of litter disturbance and diversity. The red circle indicates my primary response variable, dashed circles represent other variables that may be correlated, and lines represent mechanisms behind the proposed effects.

The first part of my research takes place in the BiodiversiTREE experiment at the Smithsonian Environmental Research Center (SERC) near Annapolis, Maryland. Seven years ago, this experiment was planted with native trees in plots of either multiple tree species (polyculture) or only one tree species (monoculture).

Satellite imagery of BiodiversiTREE, a tree diversity experiment. Each yellow dot indicates one of my research quadrats within a 35 x 35 meter monoculture or polyculture tree plot.

My project began last September when I placed 24 research quadrats in both polyculture and monoculture plots. Each quadrat was divided with deer fencing into four 1x1 meter quarters for different leaf litter disturbance treatments. After the leaves had fallen, I collected and weighed leaf litter from each quadrat. Then I divided the leaves into four quarters. One quarter was mulched through an electric leaf mulcher for the mulch treatment, two quarters were combined for the addition treatment and the last quarter was left unchanged for the control treatment. Then I returned each quarter to the quadrats from which they were collected.

Here I am surrounding a quadrat with deer fencing to separate the litter treatments and prevent leaves from blowing away.

Here we are collecting leaf litter from a quadrat for processing.

The four leaf litter treatments (Clockwise from top left): Removal, Addition, Mulch, Control.

I took temperature readings in each treatment throughout the winter. Then in March, I set up emergence traps to capture any insects which had been overwintering in the plots. Now, I’m collecting from these traps every two weeks. The next step is to begin identifying my insect collection. This is no small task, so I will first focus on butterflies, moths, and insects that control pests.

Emergence traps are set up in each quadrat. After insects emerge from the forest floor, they fly into the top bottle, the highest and brightest point. Then they exhaust themselves and drop into the lower bottle which is filled with alcohol. I switch out the lower bottles every two weeks.

The second stage of my research is very similar to the SERC study, but will take place in volunteer homeowner’s yards. I will be comparing overwintering insect emergence in yards that rake and remove their leaves with yards that retain their fallen leaves. If you are interested in being involved in this study, please click the button below for more information.

I am impressed with how successful my research has been so far. I remember feeling overwhelmed at the scale of the project less than a year ago. Since then I have mowed five foot tall golden rod, hammered over 300 PVC pipes into the ground, and constructed 100 emergence traps from scratch- all while taking classes and teaching. But while it has been difficult, I feel a great sense of accomplishment. Now with spring comes a momentary break.  I am thankful that my loved ones are safe and my research has not been drastically interrupted. I know many less fortunate. As I collect bottles from my emergence traps, I take the time to notice the flowers and the busy bees getting to work.

By Max Ferlauto, Master’s student

Graduate student funding successes

Huge congratulations to all those who were awarded funding through NSF’s GRFP program. Our lab is fortunate to have two such awardees, Kristin Jayd and Max Ferlauto!!

Kristin will be starting the Entomology Master’s program in Fall 2020. She will be looking at parasitoid wasps and their relationships via morphology, molecular analysis and museum curation. Max is a current Master’s student studying leaf litter management practices on overwintering insects.

Max has also won a couple of other awards this spring: the Smithsonian Graduate Student Fellowship and the Joan Mosenthal Dewind Award through Xerces Society.

Good luck to both of you. We are proud of the work you’ve done so far and can’t wait to see what else you’re able to accomplish in the coming years!

Ode to Oaks

Having lived on the east coast for 2 years now, I am mostly adjusted to its geography and environment. Occasionally, though, I still get struck by something and go back to experiencing the wonder of everything for the first time. One of the things which still strikes me is how awesome oak trees are.

Before moving here, I had lived in drier climates where trees are generally few and far between. After I arrived, I loved going for hikes in places like Rock Creek Park because it gave me the feeling of being enveloped in a forest. Then I started learning more about the individual identities of the forest constituents, and I loved the trees even more. I loved how the tulip trees shot up straight to the canopy before branching, how the showy magnolia flowers perfumed the air, and how the silvery smooth bark of beech trees looked almost alien.

Tulip tree near Glover Archbold Trail in northwest DC. Photo credit: K. McGurrin

Southern magnolia blossom. Photo credit: Famartin, CC BY-SA 4.0, via Wikimedia Commons

Bark from a beech near Soapstone Valley Trail in northwest DC. Photo credit: K. McGurrin

Then this past summer, I fell love with oaks. They are the most common hardwood trees in the northern hemisphere, with at least 60 species in the United States. This diversity is also increased by the fact that species often hybridize – even with molecular techniques it can be hard to unequivocally label a given tree. They are hardy specimens prized for their size, beautiful branching shade, and the durability of their lumber. In fact, in 2004 the oak tree was officially named America’s national tree. One of the most famous American oaks lived nearby in Wye Mills, Maryland for an estimated 460 years. Moreover, oaks support a wide variety of wildlife. Birds nest in their branches, beetles live under their bark, large animals (including humans) eat their nutritious acorns, and innumerable insects eat their foliage. Even after they die, oaks continue to provide shelter and nutrients for the creatures around them in the form of hollow trunks and decaying logs.

Willow oak in the Cathedral Heights neighborhood of DC. Photo credit: K. McGurrin

The amount of invertebrate life sustained by oaks was immediately obvious while we were sampling caterpillars at BiodiversiTREE this year. We visually searched on trees of 16 species of tree for 4 minutes, yet the number of caterpillars found within those 4 minutes varied dramatically among tree species. For example, dogwood and white oak trees in our experiment are about the same size, yet we found more than 3 times as many caterpillars on the white oaks as the dogwoods. The individual tree with highest abundance and diversity of caterpillars was a cherrybark oak (closely related to Southern Red Oak). On that tree we found 17 caterpillars of 8 different species in just 4 minutes! These results are in line with what Dr. Doug Tallamy reports, that the oaks support more species of Lepidoptera than any other genus in eastern forests. In addition to the caterpillars, there are plenty of other insects which eat oaks, their predators and parasitoids, so on and so forth. We actually had a hard time collecting leaves to feed to our experimental caterpillars back in the lab because every time we thought we’d removed all the extra hangers-on from the leaves, we’d flip the branch over and find another.

Above: Examples of caterpillar species found on oaks. Below: Total number of caterpillars found on different tree species at BiodiversiTREE throughout the summer of 2019. Sampling for each tree species consisted of searching 36 individual trees for 4 minutes each. Oak species are highlighted in red.

So when you want to wax poetic about America’s national treasures, don’t forget the oaks! If you have a yard, you can also do your part to support wildlife by planting an oak. The cheapest and easiest way to plant one is by collecting acorns off the ground around existing trees. Members of the white oak group even germinate in the fall, so you can be sure that you’re collecting viable seeds by looking for a little root sticking out. Come spring, acorns of all types will send up shoots, and with a little love (in the form of watering, mulch, and deer fencing) your tree will soon grow into a national treasure.

Written by Kelsey McGurrin, lab manager

A Very Hungry Caterpillar

The Very Hungry Caterpillar is a classic children’s book by Eric Carle. If you’ve ever wondered what the caterpillar would look like in real life, I imagine it would look like the larva of the Polyphemus moth, Antheraea polyphemus. The moth is named after the Cyclops named Polyphemus described in Homer’s The Odyssey.

Adult male polyphemus moth (Credit: University of Florida)

Polyphemus moths belong to the family Saturniidae, as they are considered silk moths, along with Luna moths, Cecropia moths, Io moths, and many others. These caterpillars are all fairly similar looking, but the polyphemus moth is distinguishable by the thin white stripes that it has running vertically down its sides.

This summer our lab found 2 polyphemus caterpillars while sampling at the Smithsonian Environmental Research Center (SERC) BiodiversiTREE experiment in Maryland, one at the beginning of summer and one at the end of summer. The polyphemus we found at the start of summer was likely in its first or second instar, and was found on a Black Oak (Quercus velutina) tree in a 12 species polyculture. The second one we found was in its last instar, and was found on a White Oak (Quercus alba) tree in a 4 species polyculture. This seems pretty typical, as these critters will eat a large range of trees: oak, maple, willow, elm, sycamore, and many more. And boy, do they eat a lot of leaves. We would have to put in 3-5 large oak leaves for these caterpillars, and those would last about a day and a half before being completely devoured. I didn’t compare these guys to The Very Hungry Caterpillar for nothing!

Early instar caterpillar that the sampling team found in June (Credit: Burghardt Lab)

Action shot of the same caterpillar a few months later. Nowhere close to his final size… (Credit: Burghardt Lab)

Final instar polyphemus caterpillar found in late August (Credit: Burghardt Lab)

Surprisingly, the final instar of the polyphemus was much harder to find than the first instar that we found. It most likely had to do with the fact that the caterpillars get so big - the one we found was probably as large as my pointer finger! Because the caterpillars are so large and have a green cryptic coloration, it’s pretty easy to see how predators may confuse the polyphemus for a leaf. Our lab almost made that same mistake! 

Unfortunately, the large size of these creatures means that they’re an easy target for parasitoids and other natural enemies. Tachinid flies are common parasitoids, as well as several species of wasps. The caterpillar in the picture below was one we collected and sure enough, several weeks after it pupated, flies emerged instead of an adult moth. The polyphemus moth normally overwinters as a cocoon, so we are still waiting to see if our first larva will successfully emerge as an adult or not.

If you look closely, you can see some black parasitoid oviposition holes on the second segment behind this critter’s head! (Credit: Burghardt Lab)

A closeup of one of the parasitoid Tachinid flies that emerged from the caterpillar above (Credit: Burghardt Lab)

Written by Elizabeth Butz, undergraduate student

Our first blog post!

Stay tuned for updates to our new lab blog, where throughout the course of the year different people will take turns contributing content. To start us off, here is a performance by the “Mighty Sound of Maryland” marching band, featuring our very own Elizabeth (mellophone) and Zoe (piccolo)!