Insects – Page 3 – Maryland Grows

Research Update from the Serpentine Grasslands: Pollinators in a Rare and Endangered Habitat

April 8, 2024April 4, 2024Maryland GrowsLeave a comment

Did you know that before European colonization and thanks to native land management, the area that is now northern Maryland was home to thousands of acres of sprawling prairie-like grasslands? It’s a pretty cool thing to imagine, right? Instead of dense urban centers, highways, farms, and patches of forest, most of Baltimore County would’ve been a nearly treeless ocean of swaying grasses and wildflowers! Instead of cars, shopping carts, and the hustle and bustle of people, you’d see majestic herds of deer and elk, a horizon dotted with flocks of birds, and the busyness of bees and butterflies. You can read more in a previous blog post about these eastern ‘Serpentine Grasslands’. Sadly, these grasslands no longer exist in the formerly massive extent they used to occupy, but several preserved remnants still endure here in Maryland to tell the tale of their former glory!

a view of the Maryland Serpentine Grasslands on a cloudy day — *A stormy summer evening at Soldiers Delight Natural Environment Area, Baltimore Co. – one of Maryland’s Serpentine preservation areas. Photo: Justin O’Neill*

What is the current status of the Maryland Serpentine Grasslands?

Many historic and contemporary human-driven environmental changes have caused these special ecosystems to dwindle to the point of concern; it is currently estimated that only 1.6% of their historic area in the region remains. This precipitous decline of eastern Serpentine Grasslands is concerning because they support many special plant species that are considered threatened or rare in Maryland. Luckily, several private and governmental organizations have taken to conserving and studying these ecosystems in Maryland and elsewhere (check out some of them here: Soldiers Delight and Lake Roland). Although eastern Serpentine grasslands have attracted considerable scientific research interest in terms of their rare and unique plant life, the animals that call these critically imperiled habitats home are virtually undocumented (with the exception of some rare butterflies and moths). Could there be special Serpentine associated species that we have yet to even notice?

a purple wildflower found in the Maryland Serpenine Grasslands — Phemeranthus teretifolius, the Quill Fameflower, is one of the special plants that makes its home on the dry and rocky soils of Serpentine habitats. The flower is only open during a few short hours in the afternoon, during which it is abuzz with small solitary bees. Photo: Justin O’Neill

The mission of knowing what lives there to better protect it

To address this knowledge gap, our team at the EspíndoLab, have set out to start documenting the insects present in Maryland’s Serpentine Grasslands. Our current focus is on flower-visiting insects that could act as pollinators, specifically bees and hoverflies. Given the many rare and threatened plants documented in these areas, we figured it was important to first know what insects might be helping most with Serpentine plant reproduction.

How do we do this?

To document these flower-visiting insects, the lab crew has undertaken 5 years (2019 – 2023) of observations and insect collection in three of Maryland’s most intact Serpentine Grassland conservation areas. Because different flowers bloom during different parts of the growing season (spring to fall), we had to visit these conservation areas many times each year to observe the full range of flowering plants and their insect visitors. So, once every two to three weeks across each season, the Serpentine squad would head out to visit our many field study sites and systematically capture bees and hoverflies seen interacting with flowers. Currently, we are working on the meticulous process of examining each captured specimen with a microscope to determine its species identity using taxonomic guides.

a student researcher collecting insects at the Maryland Serpentine Grasslands — Nets at the ready! The Serpentine squad carefully captures bees and hoverflies seen visiting flowers at several study sites across three of Maryland’s Serpentine conservation areas. Photo: Justin O’Neill

With this information we can begin to catalog the insect species that make up Serpentine pollination communities. This allows us to explore if the communities present in the Serpentines are different from those in nearby habitats and if they possess any rare or unique species. This information will also give us insight on how the plant and pollinator communities interact with one another; informing us about key species that contribute vitally to pollinator persistence or plant reproduction. Ultimately, the knowledge we gain will provide a baseline understanding about the dynamics of pollinator diversity in the grasslands and inform the organizations that conserve and restore these ecosystems.

What are we learning?

So far, the EspíndoLab’s efforts in the grasslands have revealed quite a bit about the broad array of insects that visit these unique plant communities. Notably, among the myriad of beetles, butterflies, flies, and wasps that visit Serpentine flowers, native solitary bees and hoverflies are consistently observed to be the most abundant – and perhaps most important potential pollinators. Interestingly, social bee species, particularly honey bees, that are commonly observed in many pollination communities, were infrequently encountered in our collecting efforts until late in the season, if it all. This suggests that they may pass on the relatively sparse floral resources of the grasslands until the Fall, when dense and attractive patches of goldenrod and aster bloom – potentially providing them an important source of resources as pickings become slim late in the season.

Most excitingly, our collections have revealed 39 unique genera of bees and hoverflies in the grasslands, so far – with more likely to be found as we continue to identify the many insects from our collections. Our efforts have also found several rare bee and hoverfly species; some of which are insects that have never been observed in Baltimore County! Among these rare and interesting finds are two bees and a hoverfly that are particularly special.

The hoverfly, Trichopsomyia litoralis, is relatively new to science – having only been described in 2019. Not much is known about the ecology of this species, but its larvae are known to feed on economically important pests. Encountering this species in the Serpentine grasslands is interesting not only because it is rarely observed, but also because it is currently thought to only inhabit an eastern coastal range (likely associated with sandy sites)! This information could extend our understanding of this hoverfly’s distribution or suggest that these flies undertake long migrations during their life cycle.

On the other hand, we have found two rare bee species that are really cool: the mining bee, Andrena gardineri; and the nomad bee Nomada seneciophila. These bees are what we call specialists: they have very specific ecological requirements. For example, A. gardineri is known to preferentially forage for pollen on plants from the genus Packera (ragworts or groundsels) – it is considered a Packera specialist. Even though A. gardineri is quite rare in the region, we find it commonly during our spring grassland collections. This is because almost all the conserved grassland areas provide good conditions to host lots of Packera anonyma.

close-up of the face of a bee found in the Maryland Serpentine Grasslands — *A close-up shot of a fluffy male Andrena gardineri specimen. Photo: USGS Bee Monitoring Lab / Brooke Alexander.* *CC 2.0*

The other notable bee we observed, the nomad bee, Nomada seneciophila is a vanishingly rare cuckoo bee (see here what these bees do and why this is fascinating). These bees wander (nomadically so) around in search of other bee’s nests so they can hijack them for their own young to develop in! N. seneciophila, as it turns out, is a specialist of our specialist friend, A. gardineri. That is, this nomad bee species has a very strong preference for stealing the nests of our other rare bee, A. gardineri!

another bee found in the Maryland Serpentine Grasslands — *The waspy-looking Nomad bee: Nomada seneciophila. Photo: Justin O’Neill*

From these interesting encounters, it is becoming increasingly clear that these grasslands not only support remarkable plants; they also provide critical resources and nesting habitat for rare bee and hoverfly species. Although these once expansive ecosystems might not exist on the grand scale they once did, their remnants are unique contributors to the region’s biodiversity. Taking the time to document their floristic and faunistic wonders is important for understanding the historic role they played in shaping regional biodiversity today, and how that biodiversity may respond to the changing environments of the future!

By Justin O’Neill, Ph.D. student, and Dr. Anahí Espíndola, Assistant Professor, EspíndoLab, Department of Entomology, University of Maryland, College Park.

Stem-Nesting Bees in Maryland

March 11, 2024March 8, 2024Maryland Grows1 Comment

With their large diversity, bees display a huge variety of nesting preferences. Some bees that are relatively commonly encountered in our region are those that nest in stems. In today’s post, I want to tell you about who they are, their biology, and their preferences when the time comes for them to pick their nesting sites.

Who are the stem-nesting bees in our region?

When we consider bees that nest in stems, we can think about two main groups. In the first group, we have bees that actively dig into pithy stems or wood to build their galleries. In the second group, we have those that use pre-existing cavities in stems and slightly adjust them to accommodate their brood. This difference may seem trivial; at the end of the day, they will all end up in stems, right? Well, that is true to some extent; however, whether we talk about one group or the other will define what actual taxonomic group of bees we’ll be referring to, and a different set of morphological adaptations that allow them to build their nests properly.

In our region both types of bees are present and many of them are relatively common and easily observed in our green spaces.

Stem nesters that dig their nests

In addition to large carpenter bees (Xylocopa), this group includes Halictid bees such as Augochlora and the Apidae Ceratina. Because they all have to dig actively into stems to build their nests inside, all these bees are equipped with very strong mandibles, which have modifications that reinforce them, and strong muscles that allow them to increase the force they can exert on the stems.

a metallic green bee going into a stem nest cavity — Metallic bees are very common in our region. They often can be found emerging or looking for wooden resources to build their nests. Photo: K. Shultz (CC).

Depending on the species, we can find them building nests on different substrates. While Augochlora can often be found building galleries in rotten logs, Ceratina is mostly associated with stems that tend to be a bit hollower, such as those of raspberries and blackberries (you can check out this other post on how to trim those plants to protect their nests), or those of plants of the genus Verbena. In all these cases, the nests have the shape of a gallery, with small cells built consecutively. Each of these cells is carefully built, provisioned with nectar and pollen, populated with one egg, and finally sealed with sawdust or compacted pith.

Stem nesters that use stem cavities that already exist

Several families of bees belong to this group in the Mid-Atlantic. Species of the genus Hylaeus in the family Colletidae are present in our region, and readily nest in hollow stems. Another group that is very commonly seen in our region is that of leaf-cutter bees (Megachilidae). Although this group tends to be more flexible in the types of cavities they will use for building their nests, many species will readily use natural or artificial “stem-like” cavities (these bees are very common in bee hotels).

several bees nesting inside of a plant stem — A small bee commonly seen in bee hotels is that of genus *Hylaeus*, also known as the yellow-faced bees. These bees will readily use small hollow stems and cavities. Photo: R. Cruickshank (CC).

Stem-nesting bees (Hylaeus) were observed in a raspberry cane on May 10, 2023, in Montgomery County, MD. Video: Christa Carignan, University of Maryland Extension

Because these groups do not need to actively dig into wood to build their nests, their mandibles are not as developed as those of the other group of bees I presented above. A common characteristic of all these bees is that they have relatively long and slender bodies, which is believed to allow them to move with more ease in relatively small cavities. It is also for this reason that specialists think that all these species transport pollen either internally or on the lower part of their abdomens (instead of on their legs, for example); this reduces their “width” and allows them to fit into cavities that may otherwise be too narrow. Another characteristic of this group of bees is that they often line their brood cells with special materials, such as leaves, petals, resins, or mud. This means that building these nests is a lot of work!

leaf-cutter bee carrying a leaf piece to a nest — Leaf-cutter bees of genus *Megachile* are also very commonly seen in bee hotels and nesting in cavities around our homes. Here, *M. centuncularis*, brings leaf cuttings to line the nest in a cavity offered in a bee hotel. Photo: B. Plank (CC).

Although bees (and most insects) are generally negatively affected by urbanization, this group of bees appears to benefit from their interactions with humans. Unlike ground-nesting bees which are very negatively affected by land development and urbanization, it seems that stem-nesting bees can easily use many cavities created by humans, such as those appearing in buildings, walls, fences, and gardens.

Read more: This Year, Host Bees in Your Garden

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an award-winning Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Help us improve the Maryland Grows Blog! Please complete our brief survey to give us your feedback and let us know about your interests.

A Little-Known Group of Pollinators: Beetles!

February 12, 2024February 12, 2024Maryland GrowsLeave a comment

As we mentioned in previous posts, when we think about pollinators, we tend to think of butterflies and bees, but rarely about the super important hoverflies or other groups of organisms. In today’s post, I want to tell you about another of those little-known pollinator groups; let’s talk about beetles that act as pollinators!

Beetles: “hard-shelled” pollinators

From a taxonomic perspective, beetles are a group of insects that belong to the Order Coleoptera. Among other important characteristics, they are recognized by their extremely well-protected body, in particular by structures called “elytra”, which provide a very hard cover to their wings (the wings are placed under the elytra). Generally, beetles have mouth parts that are adapted to chewing, which means that they have large mandibles that allow them to break their food. You may be wondering why I am talking about these structures in a pollination post… well, as for all pollinators, the shape and function of a pollinator define what they do (and don’t do). Let’s see how this affects our pollinating beetles.

a black and yellow beetle on a purple flower — Beetles are common flower visitors, with some of them being very effective pollinators. Because of their very well-protected bodies (see elytra covering the “back” of this beetle), they often spend a lot of time on flowers, where they feed on pollen, nectar, and floral parts. In this picture, we can see a cetoin scarab beetle with prominent elytra and a very hairy body that helps them transport pollen grains between flowers. Photo: C. J. Sharp (CC).

In the case of beetles, the fact that they are well protected by those elytra makes them more “confident.” That “hard shell” provides a great deal of protection against predation by other arthropods, which in turn makes them generally more “chill” in their visits to flowers. Unlike butterflies, bees, or hoverflies, beetles tend to move little within and between flowers, taking all their time to get the resources they need from them. For this reason, they are often considered as more generalist and inconsistent pollinators than their less-protected counterparts.

The shape of their mouths and their feeding habits also affect their efficiency as pollinators. In fact, beetle visits to flowers tend to be relatively destructive because they are attracted to them by their floral tissues, including in some cases pollen and the ovaries! In this respect, beetles tend to visit flowers to feed on them, which in some cases can lead to floral destruction. So, given this, are beetles good pollinators or just flower herbivores?

Beetles as pollinators

Among all the many different groups of beetles, some of them are considered to be particularly good pollinators. Specifically, these belong to the beetle families known as soldier (family Cantharidae) and longhorn (family Cerambycidae) beetles, families that depend on floral resources for their survival at least at one stage of their development. Other families such as scarabs can also be strongly associated with flowers for their survival. In all these groups, the beetles in question have clear adaptations that make them good agents of pollen transfer. For example, we observe different parts of their bodies covered with abundant hairs. This improves pollen transport and thus increases their ability to effectively cross-pollinate the flowers they visit.

a beetle with pollen grains on its head — Beetles that are good at transporting pollen have hairier bodies that can carry pollen grains, like this cantharid beetle that got its face covered in pollen while visiting these flowers. Note the yellow “powder” – pollen – that covers part of the beetle body and take a look at the large mandibles the beetle uses to feed on floral parts. Photo: J. Tann (CC).

Further, although these beetles tend to still feed on floral parts, they are usually much less destructive than their more generalist cousins. They often feed on specific flower parts (instead of on all the floral sections), leaving the central reproductive structures (e.g., the ovaries) intact, and thus allowing plant reproduction. These beetles are also often more specialized in their floral choices, preferring a small range of plant groups (usually one or a few species within the same plant genus), and moving more readily between flowers. Combined, all of this means these beetles can not only carry a lot of pollen (they are hairy) but also move it from flower to flower more effectively and do not destroy completely the flowers they visit.

A cool beetle pollination example

Beetle pollination is a very understudied topic in temperate regions such as Maryland, and we are still learning a lot about it. It is thus not surprising that the number of examples from our region is not super high. Let’s talk about one of them that happens to be relatively well-studied elsewhere but that also occurs in North America.

yellow and black soldier beetle on a magnolia flower — Beetles are considered some of the most important pollinators of species of the genus *Magnolia.* Here, a long-horned (Cerambycid) beetle on a *Magnolia grandiflora* flower. Photo: D. Hill (CC).

An example of beetle pollination of native plants that are also present in our region is that of Magnolia flowers. Although most of our knowledge on the pollination of this plant genus comes from studies done on species outside of North America, there are a couple of reports of floral visitors in several of our local species. From elsewhere, we know that these trees display flowers that appear to be particularly attractive to beetles: they are white, easily accessible, offer a lot of pollen, are fragrant, and in some cases even produce heat! In many of these species, the flowers appear to attract scarab beetles, which, once landed on the flowers, feed on the petals, mate, and then actively move between flowers and cross-pollinate. In North America, some studies like this one and this other one (in PDF) have found a wide variety of beetles attracted to our native species. Many of these beetles are very small and visit Magnolia flowers to feed on them, mate, and spend the night protected within the flowers.

By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park. See more posts by Anahí.

Anahí also writes an Extension Blog in Spanish! Check it out here, extensionesp.umd.edu, and please share and spread the word to your Spanish-speaking friends and colleagues in Maryland. ¡Bienvenidos a Extensión en Español!

Help us improve the Maryland Grows Blog! Please complete our brief survey to give us your feedback and let us know about your interests.

Ground Beetles: How to Support These Garden Helpers During the Winter

December 15, 2023December 18, 2023Maryland Grows2 Comments

Do you ever wonder where insects go during the winter? This year, as you snuggle up under a warm blanket to escape the winter cold, think about how you can help the beneficial insects in your garden do the same. The harsh conditions of the cold season can be challenging to deal with, but some insects can benefit from habitats that provide them with shelter not only during the winter but all year round. Ground beetles are a great example of insects that can be a tremendous help in the garden, but also appreciate a good nook or cranny to hide out in while the weather is less than ideal.

Ground beetles are one of the most diverse insect families in the world and can be found in many shapes and sizes across Maryland’s gardens, farms, and natural areas. Like butterflies and moths, ground beetles go through a complete metamorphosis, changing drastically in appearance throughout their life cycle. They begin their lives as larvae that resemble small, fast-moving, armor-plated caterpillars with giant mandibles – a little intimidating, but luckily, they’re on your side! Ground beetle larvae mostly feed on other small invertebrates, including a range of garden pests like aphids, grubs, and caterpillars. Ground beetles generally spend a few months as a larva and can live several more years as an adult.

ground beetle larva preying upon another insect in the soil — Ground beetle larva with a potential snack. Photo: Benjamin Burgunder (CC-BY)

Adult ground beetles can be anywhere from ⅛ to 1 ½ inches long and oval-shaped with a plain dark coloration, but some may sport a green or bronze iridescence. They have long legs and thread-like antennae. Like other beetles, they have hard wing covers, usually with prominent ridges running across their length. These wing covers protect hind wings that may sometimes be used to fly, but many species have lost this ability. Even those that retain it are more likely to be found running across the ground or burrowing down just underneath the substrate.

Ground beetles have large, powerful mandibles that they use to capture and chew their food, which they’re not picky about. They are well-known for eating a wide variety of foods, but many species have a preference for one type over another. Some species, including Chlaenius aestivus, Scarites subterraneus, and Poecilus chalcites are famous predators of other invertebrates including aphids, caterpillars, and slugs, and can help keep pests at bay in your garden. Other species such as Amara aenea, Harpalus pensylvanicus, and Anisodactylus sanctaecrucis also feed on other invertebrates, but have additionally been studied for their useful tendency to eat the seeds of common weeds, helping to manage these weeds before they even start growing.

4 different species of ground beetles — Some common ground beetle species in Maryland include insect pest predators *Chlaenius aestivus* (top left) and *Scarites subterraneus* (top right), as well as weed seed eaters *Amara aenea* (bottom left) and *Harpalus pensylvanicus* (bottom right). Photos: Zachary Dankowicz, Debbie Johnson, Martin Galli, Don Marsille (CC BY-NC)

While ground beetles do not damage garden plants, they may be considered a household pest if found wandering through homes. Most ground beetles are nocturnal and attracted to lights, so they may inadvertently enter houses and have trouble getting out. In this case, simply use a cup and a piece of paper or your hands to capture them. They do not pose any significant danger to you or your pets, but if handled roughly, their mandibles may deliver a small pinch. Relocate them outside where they can continue to serve you and your garden.

If you want to help support these useful critters, there are several actions you can take.

Avoid practices that disturb soil fauna such as frequent tillage, and don’t use broad-spectrum insecticides, i.e. those that harm a wide range of insects including beneficials.
Don’t leave the ground bare. Bare earth does not provide the best protection against the cold, so cutting back your plants before or during the winter to tidy up your garden actually may be harmful to resident ground beetles. Applying a straw mulch can help cover up bare earth and provide shelter for these overwintering insects. Planting perennials in or near your garden can also provide a lasting habitat for beneficial insects. Establishing stretches of perennial grasses called “beetle banks” is a common technique used to increase ground beetle numbers on farms in many places around the world.
Create sheltered spaces. Ground beetles will even hide out underneath large stones, logs, or brush piles. In addition to helping ground beetles, creating sheltered habitats and leaving ground cover over the soil can also help other beneficial insects, including pollinators and insects that are important food for birds (“leave the leaves!”).

straw mulch placed around plants in a vegetable garden — In addition to helping with soil moisture retention, temperature regulation, and weed control, applying a lightweight mulch such as straw may provide shelter for ground beetles and other beneficial insects. Photo: https://extension.umd.edu/resource/what-organic-or-sustainable-vegetable-gardening

Because they can live for several years, helping ground beetles for one year can result in much greater numbers during the following years as well. It’s an investment in your garden’s natural defenses against pests! Having these predators around can help keep you from needing to resort to using pesticides which may be harmful to your health and to the environment. Next time you’re making plans for your garden, consider helping out your garden’s natural protectors and enjoy as they return the favor.

References

Dennis, P., Thomas, M. B., & Sotherton, N. W. (1994). Structural Features of Field Boundaries Which Influence the Overwintering Densities of Beneficial Arthropod Predators. The Journal of Applied Ecology, 31(2), 361. https://doi.org/10.2307/2404550

Jordan, S. F., Hopwood, J., & Morris, S. (2020). Nesting & Overwintering Habitat for Pollinators & Other Beneficial Insects. The Xerces Society for Invertebrate Conservation.

Lövei, G. L., & Sunderland, K. D. (1996). Ecology and Behavior of Ground Beetles (Coleoptera: Carabidae). Annual Review of Entomology, 41(1), 231–256. https://doi.org/10.1146/annurev.en.41.010196.001311

MacLeod, A., Wratten, S. D., Sotherton, N. W., & Thomas, M. B. (2004). “Beetle banks” as refuges for beneficial arthropods in farmland: Long-term changes in predator communities and habitat. Agricultural and Forest Entomology, 6(2), 147–154. https://doi.org/10.1111/j.1461-9563.2004.00215.x

Philpott, S. M., Albuquerque, S., Bichier, P., Cohen, H., Egerer, M. H., Kirk, C., & Will, K. W. (2019). Local and Landscape Drivers of Carabid Activity, Species Richness, and Traits in Urban Gardens in Coastal California. Insects, 10(4), Article 4. https://doi.org/10.3390/insects10040112

Philpott, S. M., & Bichier, P. (2017). Local and landscape drivers of predation services in urban gardens. Ecological Applications, 27(3), 966–976. https://doi.org/10.1002/eap.1500

By Alireza Shokoohi, M.S. Student, Department of Entomology, University of Maryland, College Park.

How Do We Study Pollination?

December 11, 2023December 11, 2023Maryland GrowsLeave a comment

Pollination is such a buzzword right now, and a lot is said about pollination and pollinators. However, how do people learn about pollination and pollinators? How do people know who the pollinators are and how pollination works? Because I happen to do research on pollination, I wanted to use this opportunity to share with you some insights into how pollination is studied, what it teaches us about plants and their reproduction, and how this connects with the things we hear about pollination.

What are we studying when we study pollination?

As we mentioned in previous posts, pollination is basically how plants reproduce. Generally, pollination involves the deposition of pollen grains on the female organs of a plant, which in many cases leads to ovule fertilization and often the production of seeds and sometimes fruits. So, when we study pollination, what we are studying is the reproductive strategies of plants. If we think about plants and the many different ways they have to reproduce, it may be simple to imagine all the different aspects one can try to understand about pollination. Here I will present a couple.

The reproductive strategy of plants – selfing, crossing, or both?

Unlike us humans, many plants can self-pollinate. This means that the species that can do this can technically accept pollen from their own flower and use it to fertilize their own ovules. The consequence of this is that plants that can self-pollinate do not necessarily need pollen from another individual to produce offspring. This may seem like a nerdy technicality of mine, but the ability or not of a plant to self can have a lot of wide-ranging consequences. From an evolutionary perspective, this can affect the genetic diversity in a species or group of species, which can define whether a species can adapt or not to certain conditions, among other things. This can also have consequences for food production and plant breeding; if a plant cannot self, several stocks need to be present in a field for it to be able to produce fruit. This for example happens to some varieties of cherries, where more than one tree needs to be planted in an orchard for the plants to produce fruit.

reproductive parts of flowers — To test for plant reproductive strategies, researchers can perform controlled crossing experiments, which follow generally what is presented in this figure. Image: University of Waikato.

To understand whether a plant species can self, a basic experiment can be done. In this experiment, one creates groups of plants of the same species that will be pollinated following different methods. By comparing the number of seeds produced by each method, one can infer how the plant reproduces. In its simplest forms, one of these experimental groups of plants is manually selfed, which usually involves removing all anthers from a flower and then manually depositing pollen from the same plant on its stigma. In another group, plants are crossed using pollen from another plant. The flowers and potentially fruits of both groups of plants are then left to develop, and once fruit/seed maturity is reached, one counts the number of fruits and seeds per group of plants. If the two groups present significantly different numbers of fruits or seeds, then we can infer whether the plant is able or not to self.

Who pollinates a plant?

Imagine that we figured that a plant requires cross-pollination. Now, a question we may want to ask is how the pollen of one flower can get to the stigma of another flower. Again, this is not just a biologist niche question; this has practical and evolutionary consequences. For example, if a plant is wind or water-pollinated, it will be able to produce offspring in the absence of animal pollinators. Alternatively, if a plant needs animal pollinators, then their absence can lead to the plant’s inability to sustain its population over time. In a food production world, plants that need animal pollinators will benefit from the presence of those pollinators, leading to higher fruit or crop production when more pollinators are present (this is the case of, for example, almonds and strawberries).

To study this, scientists have a large palette of methods. Here are some. One of them involves observation of the flowers in question. For example, one can assume that a flower that produces nectar or that has special color markings aimed at directing pollinators when they visit a flower will be more likely pollinated by animal pollinators than one that does not offer any floral rewards in exchange for flower visitation. Similarly, the general floral shape gives clues about how it may be pollinated. Flowers pollinated by animals tend to have specific shapes that improve pollen deposition by animal visits, while those pollinated by abiotic factors are usually droopy or displayed in very humid areas.

markings on flowers only visible with UV light — Flowers that can look “plain” to us may have special colorations that only pollinators can see, like this black-eyed Susan, which shows its floral markings that can be seen only under UV light (a wavelength many insects can see). Observing markings or “signs” on flowers indicates that the plant may use animals for pollen dispersal and transfer. Photo: A. Davidhazy.

As said before, observations are a huge part of studying pollination and the identity of pollinators of a plant. This generally also entails spending hours upon hours over several seasons carefully observing and sometimes capturing any floral visitor and potential pollinator of a plant population. This requires patience and focus, and careful recording of the abundance, frequency, and identity of any flower visitor. This also often requires hours of identification of captured floral visitors, often under the microscope (given that most floral visitors are often insects), and through the use of taxonomic keys or the consultation of experts of specific taxonomic groups.

a man in a field using an insect sweep net — One way to understand what pollinates a plant involves hours of focused observation of flowers and capture of the animals seen visiting them. Photo: A. Espíndola.

fluroescent dyes are used to track movement of pollen by pollinators — Fluorescent dyes can be used to track the movement of pollinators and the potential for pollen transfer. Photo: Huais et al., 2022.

Along with these hours of observing and describing what is being seen, other more “manipulative” approaches exist. For example, many scientists try to understand who visits a flower by marking flowers with powdery dyes and then seeing if any animal seen visiting the flowers becomes colored with the dyes. More “technological” approaches use high-resolution cameras and artificial intelligence (AI) methods, as well as DNA sequencing to identify the presence and species identity of pollen grains on animals seen or suspected of visiting flowers.

Q&A: How Can I Get Wasps Out of My Compost?

November 6, 2023November 2, 2023Maryland GrowsLeave a comment

Yellowjacket *(Vespula sp.).* Photo: M. Talabac

Q: Wasps took up residence in my compost pile this year. I could avoid them for a while, but I’m hoping I can use the pile again next spring. How can I get them out of there?

A: Ground-nesting yellowjackets are probably the culprit here, and the good news is that they will disappear on their own by winter. In our area, social wasps like hornets, yellowjackets, and paper wasps don’t reuse the same nest for more than one year. By late autumn or early winter, the old queen, workers, males, and any juveniles that did not have time to mature will all die. Only mated young queens survive, leaving the nest of their birth to disperse and overwinter in a sheltered spot by themselves. They seek out insulated spots like hollows under fallen logs and nooks in stone walls, go into the insect version of hibernation, and emerge in spring as it warms up, each flying off to find her own site to start a new nest. She does all the nest-building and larvae-feeding work by herself until the first generation of young matures, so she has a limited ability to defend it from disturbance.

Nest remnants left in the compost pile will be abandoned (or will at least contain dead wasps) during winter, when you can safely dig it out for removal or just leave it to compost with the rest of the pile contents. Wild animals can also tear apart abandoned wasp nests, looking for easy-access morsels to snack on, though this presumably happens more regularly with visible above-ground nests.

Preventing a new generation of wasps from choosing the same appealing nest site in a future year might be challenging unless you enclose the pile in insect mesh or something to discourage queen wasps from exploring it in spring. Regular turning of the pile – recommended to keep it well-oxygenated anyway – might disturb a new queen too much to allow her to successfully begin a new nest.

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.

Goldenrods: The Garden Thyme Podcast

September 14, 2023September 13, 2023Maryland Grows4 Comments

goldenrods episode of The Garden Thyme Podcast

Gold and yellow hues are the undeniable colors of autumn. In this episode of The Garden Thyme Podcast, we discuss one of our favorite yellow-blooming perennial plants – goldenrod. With its pretty yellow flowers, long blooming seasons, and high wildlife value, what is not to love about these fantastic native plants? Mikaela also counts down her top pick of goldenrods for different gardens (~17:10). Her goldenrod bloom chart can be found here.

We also have our:

Native Plant of the Month – Pawpaw (Asimina triloba) (~22:45)
Bug of the Month – Goldenrod Bunch Gall Midge (~33:35)
Garden Tips of the Month (~39:15)

Listen to the podcast

If you have any garden-related questions, please email us at UMEGardenPodcast@gmail.com or look us up on Facebook.

For more information about the University of Maryland Extension (UME) and these topics, please check out the UME Home and Garden Information Center.

The Garden Thyme Podcast is brought to you by the University of Maryland Extension. Hosts are Mikaela Boley- Senior Agent Associate (Talbot County) for Horticulture, Rachel Rhodes- Agent Associate for Horticulture (Queen Anne’s County), and Emily Zobel-Senior Agent Associate for Agriculture (Dorchester County).

Theme Song: By Jason Inc