Author:Anahi – Maryland Grows

The more the merrier: community actions for pollinators

June 13, 2022June 9, 2022Maryland Grows1 Comment

Besides it being the month when summer starts, June is a great month because it is when Pollinator Week happens! 😊

Tagging along with that week, in today’s post I want to talk about some actions you can take with(in) your community to help pollinators! Because, if we want to help pollinators, a very valid and effective way to amplify your actions is to get others on board! Here, a non-extensive list of ideas.

1. Become a Bee City

Ask your City or Campus to become a certified Bee City or Bee Campus USA. Bee Cities and Campuses are certifications that cities and campuses across the USA can obtain if they implement a series of actions (“commitments”) established by the Xerces Society. Once these actions are done, the City or Campus in question becomes certified as a pollinator-friendly space. The types of actions outlined are really activities that lead to increasing education on pollinators and pollination, to improving pollinator habitat on the institution’s land, to promoting actions in the way that the institution functions that may allow for increasing pollinator support (see here for city commitments and here for campus commitments). Becoming a Bee City or Campus is not hard, and most institutions say yes if their members ask. If you think this is something you would like your City and/or Campus to do, reach out to your representatives or leadership and get them on board! And to have an idea of what cities and campuses are already involved, take a look at the Bee City USA affiliates.

2. Organize a Pollinator Week Event

Pollinator Week is a National event organized by the Pollinator Partnership and includes many possible actions that lead to increasing pollinator survival and/or awareness. This year, Pollinator Week will be happening June 20-26. One can participate in activities already organized by others, or one can propose and host an activity! If you would like to get together with your community and organize an event, do it, and then submit it to the Pollinator Week event list! That way, others will know about it and will participate as well! To submit (or participate in) an event, go to the bottom of the Pollinator Partnership page.

Here are some activities happening in Maryland: bee hotel building workshop in College Park, MD, webinar in Greenbelt, MD, pollinator catch-and-release in Saint Leonard, MD, and several activities in Howard Co., MD.

3. Ask your city to host a No-Mow Month in early-spring

Early-spring pollinators emerge usually when very few plants are flowering, meaning that the early spring is a critical time for these pollinators. In human-occupied landscapes like cities or suburban areas, a lot of the landscape is occupied by lawns, which can provide some flowers early in the spring. No-Mow Month (usually April or May, depending on the city’s conditions) is an action that seeks to allow the availability of the early flowers in lawns so that local pollinators can survive during the early spring. Once other plants in the landscape start flowering (usually at the end of April in most of Maryland), the lawn can be mowed with this not negatively affecting pollinators.

It is important to note that this action is based on voluntary participation, meaning that participants opt-in (instead of being mandated to do it). This action has been shown to be effective in increasing pollinator diversity and abundance in regions where it is implemented, and is not associated with excessive lawn growth because it occurs so early in the season. Further, it can be strengthened with native plantings, which can boost its effects and also support local landscapers during the reduced-mow month. Localities where the action has been implemented tend to have high adoption rates, increased nature awareness, and willingness to further support biodiversity around homesteads, with no- to very-reduced vermin occurrence.

This action usually requires some temporal amendments to City Code (e.g., to ensure that participants will not be penalized if their lawns surpass the maximum allowed height during the no-mow month) so it needs approval by City Councils. Although this may sound really complicated, it is not, and several Cities in Maryland have implemented this program very successfully during the month of April (see here for College Park, MD, and here for Greenbelt, MD), following Appleton, WI’s trailblazing action. If you think this is something you would like to implement in your community, get in touch with these cities’ Bee City USA committees so they can share their expertise, and then contact your representatives to ask them to adopt this action where you live!

4. Ask your community to establish pollinator-friendly plants and nesting resources

Communities can also support pollinators through the way they decide to landscape their land. Requesting your community leadership to implement pollinator-friendly gardens and offer nesting resources for pollinators (e.g., bee hotels, create small wild spaces) is a really good way to help pollinators at a larger scale. To do this, you can get in touch with you City/Town Horticulturist and/or Public Works people, and request this. If you would like to implement this in your neighborhood and on private land, you can coordinate with your neighbors and create plots of native plants or small nesting areas in everybody’s green spaces. A very effective way to do this in Maryland is by establishing a neighborhood Green Team. If you would like to know about how to do this, take a look at this page of recommended native plants and this list of native plants that do well in our area.

Chart listing easy-to-grow native plants that support pollinators

5. Ask you city/town/neighborhood to adopt an IPM plan

Although we tend to think about helping pollinators only by planting flowers and maybe creating nesting spaces, pollinators also can be helped by the way we manage our landscapes. For example, herbicides and pesticides can be sometimes very harmful to pollinators, or cutting plants at certain times of the year can really negatively affect them. Reducing the use of pesticides and herbicides, or changing the way we manage our own private land is one possibility. However, cities, towns, neighborhoods, schools, and campuses also manage their public lands! For that reason, they can also implement actions to manage spaces in ways that support pollinators.

chart explaining Integrated Pest Management in 5 steps

A very good way to institutionalize this is by requesting these institution to implement Integrated Pest Management (IPM) plans. IPM is a way of controlling pests and increasing “beneficial” organisms in a given space by means that reduce the use of pesticides and herbicides. These plans establish a framework that allows institutions to still control pests and diseases, while reducing the negative impacts on biodiversity that some conventional practices have. These plans can be very general or very specific, and if your institution does not have one, it may be time to ask them to implement one! To do this, get in touch with your institutional horticulturist or your government representative. Here are some examples: city, campus and school district plans.

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!

Bees to look out for: leaf-cutter bees!

May 9, 2022June 2, 2022Maryland GrowsLeave a comment

Spring is well-established and many flowers have already started to bloom. In my garden, I have seen several sizes and shapes of insects visiting flowers, going from small flower flies to butterflies, to very tiny and shiny, fuzzy large, and very large bees. And with all these flying organisms starting to come around us, I thought today would be a really good time to introduce you to some really cool bees that are very common in our area: the leaf-cutter bees!

What are leaf-cutter bees?

As its name suggests, these are solitary bees known to cut leaves (now you may be thinking, “duh, I could have guessed that without a blog post”, but bear with me!). These bees belong to a very large family of bees called Megachilidae, which is present on all continents except Antarctica and well-represented in our region.

Like most solitary bees, the female of leaf-cutter bees builds nests with small brood cells, in each of which a food provision is left and one egg laid. And this is where the “leaf-cutter” name comes from. When building their nests, many of these females line their brood cells with specific materials, in particular plant tissues. In fact, many of the species are known to cut leaves and/or petals to line their nests, using them to stabilize the brood cells, and likely to provide protection to the larva and the food provisions. In a fascinating way, it is suspected that these bees are able to exploit the antimicrobial effects of certain compounds present in these flowers and leaves, indirectly using them to protect their offspring until they finish their development in the nests.

If you ever saw neat and relatively large holes that seem to suddenly pop up on certain plants in your green spaces, it is very likely that they were made by some of these bees that may be nesting close to you! If you keep an eye out on those plants, it is very likely that you will end up seeing these busy bees carefully cutting, then rolling, and finally flying away with the neat plant circles!

Female leaf-cutter bee cutting a leaf

Leafcutter bee nest and brood cells made with leaf pieces — Megachilids are known for cutting leaves that they use to line the brood cells of their nest. Note that here the nest is in a soil mound and each brood cell is completely covered with leaves but capped and separate from the neighboring cells. In this nest, each cell contains one egg. Photo: E. Soh.

Continue reading →

Planning your garden to support specialized pollinators

January 10, 2022January 18, 2022Maryland GrowsLeave a comment

Looking out my window, as the ground is covered with snow and I am getting ready for another snowstorm coming tonight, it seems ironic that I have been spending many hours these days ordering seeds and planning my garden. While I am thankful that the winter brings some rest to the soil in my garden, planning this season brings me happy memories of the scents and buzzes in my yard during the growing days… which reminds me that I should also plan for my little buzzing pollinator friends when I plan what to grow this season. In today’s blog, I want to chat about how we can plan for many types of pollinators, with a special focus on planning for specialists and not just for generalist pollinators.

Specialist pollinators – never heard of them?

As we mentioned in a previous post, pollinators visit plants to feed on nectar and/or to collect pollen to feed themselves or their offspring. However, pollen is not just there for pollinators to feed on; pollen is central to plant reproduction, so plants tend to make it both attractive to pollinators but hard to digest. For this reason, and in order to be able to properly digest the pollen, pollinators are often specialized in their pollen choices. This is because being able to digest the compounds that plants add to their pollen to make them hard to eat requires some level of adaptation, which often involves a trade-off with the ability to eat anything. There are, of course, many levels of specialization, and, while many pollinators feed on many plant families, others are more specialized than that, and feed on only specific plant genera or even species! For us gardeners, this means that if we want to support many different pollinators, we need to make sure that we are also providing for those very specialized pollinators as well!

Luckily for us, the floral choices and pollen specialization is known to some extent for Maryland and Eastern USA bees (see this site to learn more). For this reason, we know that many specialized bees in our region are also rare or uncommon… another reason to try to provide resources for them!

Who are pollen specialists in our region?

Many known pollen specialist bees in our region belong to bee genera Andrena, Colletes, Osmia, and Melissodes, which have many species considered rare or uncommon in Maryland and Mid-Atlantic.

Continue reading →

How do pollinators find plants and flowers?

December 13, 2021December 10, 2021Maryland Grows1 Comment

As we know, pollinators help plants spread their pollen among flowers, and many plants do indeed need them to be able to reproduce and set seeds. We also know that by planting flowers and providing nesting habitats, we can help pollinators’ populations and thus assist with plant pollination. However, how do pollinators find plants? In this post, we will talk about that topic, which can help us become even better at helping pollinators and the plants they pollinate.

The big picture – pollinators need to be in the area

In order for pollinators to find plants, pollinators need to be present in the general region. In fact, although the vast majority of pollinators can move and travel from place to place, all of them have limitations on the distance they are able to travel. For example, hummingbirds can travel for miles (in Maryland, they are migratory), while large bees are able to travel relatively large distances for an insect (~500m-1km), and smaller insects will not be able to travel that far. This means that if, say, we lived in the middle of a very developed area with very few pollinator-friendly resources (few flowers, lots of cement, no green areas, etc.), planting a pollinator garden will attract few pollinators at first. This is due to the fact that it is likely that few pollinators are present in that area, and thus it will take a while for certain groups to arrive and establish in our garden.

It is for this reason that many communities tend to try to establish joint pollinator-friendly actions, and encourage many people in the region to participate (e.g., becoming Bee City USA-certified, creating “pollinator highways or corridors”). By increasing the regional number of pollinator-friendly resources, the whole region becomes more pollinator-diverse, and any supplementary action is more likely to improve pollinator support. As we talked about in a previous post, if you are interested in promoting pollinator-friendly habitat on your property, it may be a great idea to talk to your neighbors or your City, and see if others may also want to participate. In terms of pollinator-friendly activities, the saying “the more, the merrier” is very much true!

pollinator habitat sign in a garden — Pollinator-friendly actions are very effective when they are coordinated across regions. Photo: A. Kokai.

The local picture – different pollinators prefer different plants

As we mentioned in other posts, not all pollinators are made equal, and this is also true in terms of what plants will be found by what pollinators. For example, hummingbirds tend to visit tubular and reddish flowers, while syrphids prefer open flowers, and bees tend to visit flowers that they can access with their mouth parts (see this post to learn more).

These floral preferences are due to the different pollinators’ abilities to see different colors, the presence of specific attractive floral scents in different plant species, and the ability of different pollinators with different body and mouth part shapes to handle and feed on flowers, and the matching of pollinator presence and flowering time. The practical consequence of this is that if we want to help many different pollinators find their preferred plants, it is necessary to grow different types of plants in our green spaces. By doing this, we would always provide resources that will be preferred to at least one pollinator, and by providing different types of resources, we can make sure that many different types of pollinators are supported by our plants. In order to do this, there are different floral mixes that exist that allow us to plant diverse floral resources appropriate for our region, which lets us build a diverse and welcoming floral bed for many pollinators.

Planting diverse floral resources will attract many different types of pollinators. Photo: C. Celley/USFWS.

The super-local picture – pollinators need to see the plant to access it

This will sound silly, but pollinators need to be able to have access to the plant to find it. For example, if a plant is not clearly displayed or hidden by many other plants or structures, it will be hard for pollinators to find it… even if the pollinator is present in the area and the plant in question is a preferred plant. This means that for us to help pollinators, we need to make sure that our plants are findable by the pollinators. Picking appropriate parts of our green spaces to plant our pollinator-friendly plants is thus key! For example, plants that require full sun to grow should be planted in those conditions and not under the shade of other plants or behind structures.

To know what these specific conditions are, there exist several resources (for example, see this useful and simple resource (PDF) published by the City of College Park, MD). These resources allow us to pick the best growing spot for our plants, making them easily findable by their pollinator friends.

Finally, pollinators are more likely to find plants if there are several of them! This is particularly true for smaller herbs, which may not display many flowers. By increasing the number of plants planted in an area we are also making the plant species more easily findable to the pollinators.

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!

Introducing the king of fall fruits: persimmons!

November 8, 2021November 4, 2021Maryland Grows4 Comments

It’s fall, the air is starting to get crisp, you are walking and you see these strange trees. You are sure that they are trees, yet they have these fruits that look like tomatoes… but they are on a tree. What are those fruits? They look so attractive with that wonderful orange… should you harvest them? Should you eat them? Are they any good? What IS this? In today’s post, I want to (re)introduce you to these plants and their fruits, and hopefully the next time you see them you will have answers to all those questions and will know what to do. 😉

persimmon tree in a yard — In the fall, persimmon trees are recognized for their many orange fruits that look like tomatoes! Photo: P. Tain.

What are these orange fruits?

These fruits are what here in the USA we call persimmons (from the Powhatan word “pichamin”). Persimmons are the fruits of a group of trees that belong to the same family as ebony, and that can be found on a number of continents, including North America. Among all the persimmon species that exist, a number of them are edible, producing fruits in late fall. In the USA, there are two persimmon species that produce edible fruits, and one of them is native to right here in Maryland: the American persimmon (Diospyros virginiana).

Although the wild American persimmon still grows in our forests and was well-known by native Americans, who used its hardwood, consumed the fruits, and introduced them to the European colonists (see some Native American legends involving persimmons here), the American persimmons we see cultivated in orchards come from selected lines. Indeed, varieties of American persimmons have been selected, and many cultivars of American persimmons can be purchased and grown in gardens and orchards to produce fruit. Besides the American persimmon, there are also other species available for purchase, in particular the Oriental persimmon (D. kaki), which is very well-known in Europe.

close-up of an orange persimmon fruit in a tree — The American persimmon tree harbors fruits that turn orange, soft, and tend to fall when they are ripe. Photo: W. Pollard.

Although American and Oriental persimmons are edible both raw and cooked (see here for some recipes), it is important to note that the fruits are very astringent prior to ripening, meaning that they have to be ripe for them to be palatable. The level of ripening is usually shown by the coloration of the fruit (ripe fruits are orange), its softness (ripe fruits become soft to the touch), and their voluntary falling from the tree while not rotten. It is often said that persimmons need to go through a frost in order to ripen. This is in fact not accurate: unripe persimmons will simply rot after a frost; ripe persimmons will not rot after a frost and will in fact start slowly drying out, which will make them become sweeter. This may have led people to assume that frosts actually lead to ripening, while the frost will not help in the ripening of any fruit that was not already ripe at the moment of the frost.

Is it true that I need to plant more than one persimmon tree to have fruits?

The short answer is mostly no. American persimmon trees are what we call dioecious plants. This means that each plant will either harbor female flowers (which will become fruits) or male flowers (which will provide pollen for pollination and will not produce fruits). The first consequence of this is that if one plants or encounters a male plant, it will be impossible to ever harvest fruits from it. The second consequence of this is that a female persimmon flower needs to receive pollen from a male plant in order to produce seeds (and reproduce). In most wild forms of American persimmons, pollination is also required for fruit production.

small yellow flowers on a persimmon tree — American persimmon trees display small and delicate white flowers, which are either female or male. Photo: M. Beziat.

That being said, female plants of most selected cultivars of American persimmons can actually produce fruit without pollination. If they do not receive any pollen, these female flowers will still develop into fruits, which will not harbor any seeds and which will be fully edible. If one were to plant these cultivars in their garden or orchard, fruit production would not be restricted by female flower pollination.

But does that mean persimmons do not need pollinators?

Not really. Wild persimmons still need pollinators to transfer pollen from the male to the female plants. So who are these pollinators? In fact, we know relatively little about wild persimmon pollination. In terms of flowering time, American persimmons flower between May and June, and their flowers are small and white (and cute!). Floral visitors have not been extensively studied, but there is at least one study describing a large variety of wild bees (e.g., sweat bees, bumblebees, leaf cutter bees) visiting their flowers. From this respect, persimmons play a role in sustaining this group of pollinators and will benefit from their pollination services.

immature and adult moths that use persimmon trees for food — Persimmons also support other insects including many lovely moths from our region, such as Luna moths – top – and Regal moths – bottom). Photo: Askalotl, C. McClarren and A. Reagol, M. Clock-Rust.

Although not pollinated by them, persimmons also support other types of insects (and sometimes pollinators): moths! In fact, persimmon leaves are the favorite food of caterpillars of many native moths. In particular, Luna moth and regal moth (besides many others) caterpillars prefer persimmon leaves. It appears then that persimmons do not just feed us with their delicious fruits, but also feed many of these beautiful native moths, allowing for them to maintain their populations in our area!

Spooky Behaviors of Pollinators: The Curious Lives of Parasitic Bees

October 11, 2021October 8, 2021Maryland Grows1 Comment

Fall is here and along with the pumpkins and falling leaves, there is one thing that pops up everywhere: Halloween! And because I can’t add Halloween decorations to a blog post, this blog will have a “conceptual” Halloween twist. Today, I want to talk about something that may seem spooky to many, but that to me showcases the stunning diversity of (pollinators’) life. In today’s post we will talk about bees that are a bit “special”: parasitic bees! Come along and marvel with me about these incredible creatures that coexist with us right here in Maryland!

Parasitic bees? What!?

Yes, you read it right. Although most of the bees we know are solitary and build and provision their nests, there are several groups that have taken an evolutionary path a bit different from their relatives. These bees have evolved parasitic behaviors, exploiting the nests and food from other bee species, and in the process actively killing the host’s brood. Because they display behaviors similar to cuckoos, birds who lay eggs in other birds’ nests and have their chicks reared by the host parents (check out this video), these bees are known as cuckoo bees.

Parasitic (right) and non-parasitic (left) bees look very different. One of the main differences is the fact that parasitic bees do not have structures to collect pollen (like hairy legs with pockets), as we can see in these photos. Photos: J. Gallagher.

Cuckoo bees look different from non-parasitic bees

Because these bees have evolved to not collect nectar or pollen for provisioning (adults do eat nectar and pollen, though), and do not build nests, they have also lost the morphological structures that allow bees to do so. Cuckoo bees thus lack all the structures commonly present in bees that collect pollen (e.g., little pockets on their legs, hairs), and all the structures that allow bees to collect materials and build nests. Unlike non-parasitic bees, who often can lay only one egg per day, cuckoo bees can lay many eggs on the same day. This adaptation allows them to take full advantage of a suddenly-available nest they can parasitize. Finally, as one can imagine, host bees are not super happy about having other bees come and exploit their nests… and they defend them! For this reason, cuckoo bees are strongly “armored”, with thick and bulky structures that can protect the parasitic females against the likely attacks from the host bees. And, last but not least, some cuckoo bees can camouflage using body odors that are similar to the host, which allows them to enter the nests without being “smelled”. Cool, heh?

But how do they do it?

A trait common to all these bees is that they have high levels of specialization on what other species they parasitize, meaning that one parasitic species will often parasitize a relatively small group of closely-related non-parasitic bees. For this reason, there are different methods cuckoo bees use to parasitize their hosts.

Larvae in many cuckoo bees are equipped with impressive mandibles that they use to attack and kill other larvae developing in the parasitized brood cell. Look at these weapons! Image: Rozen *et al.,* 2019; American Museum Novitates.

The first main way is parasitizing brood cells that have been already closed. In this group, the females enter a foreign nest where closed cells are present, open the cell(s) where they want to lay the egg, kill the host’s egg with their sting or mandibles, then lay an egg in the (now empty) cell and close it. Other species that also parasitize closed cells are those in which the females open the cells, but instead of killing the host egg, just lay theirs in the cell before sealing it back. In this case, it is not the female but the larvae that will kill the host egg/larva. These parasitic larvae have strong mandibles that allow them to attack the resident larvae and kill them, keeping all the resources for themselves. Finally, other cuckoo species do not wait until the host cells are closed. The females of these species enter nests where cells are still open, and lay their very small and hard-to-see eggs in the open cells. The host female often oversees them and closes the cells with the parasitic egg in it. The parasitic larva develops in the closed cell and also uses its strong mandibles to attack and kill the host larva while in the cell.

Do parasitic bees exist in Maryland?

Yes! Although these life histories may seem like they are coming from another planet, we do not need to travel to exotic places to be able to encounter these species! They also occur right here!

The small Macropis cuckoo bees *Epeoloides pilosula* are very rare in Maryland and protected in most of their North American range. Photo: M. Veit.

A very cool species that is very likely present here in Maryland is the Macropis cuckoo bee Epeoloides pilosula, which parasitizes nests of the oil-bee of genus Macropis. Because of the level of specialization of both the oil-bee (on their host plant; see here to learn more) and its parasite, E. pilosula is very rarely encountered and is currently protected at different levels in Eastern North-America.

There are several species of *Nomada* or Nomad cuckoo bees in Maryland. These species often parasitize nests
of ground nesting bees. Photo: M. Lucas.

Another very neat example of local cuckoo bees are the parasites of Andrena and other mining bees: the parasitic bees of genus Nomada. The rule of lack of hairs and structures to collect provisions for the nest is very much true for this species! There are about 30 species of this genus known to be present in our state, and many of them are rare. While the spotted cuckoo bee Nomada maculata is somewhat regularly found in the state, Nomada bethunei is known only from a couple localities. Most of these Nomada species are, however, rare and often under conservation threats.

Will parasitic bees drive other bees to extinction?

Parasitic and non-parasitic bees have been co-evolving for millions of years, and it is very unlikely that this type of interaction would drive species to extinction. Indeed, the parasitized species also have evolved ways to protect their brood (something for another post). Interestingly, however, because parasitic bees are so specialized on their hosts, it is they who may be even more at risk of extinction than their hosts! Indeed, cuckoo bees are rare, hard to find, and are likely to have populations die out as soon as their host species disappears from a locality. From this respect, and if we want to protect the diversity of this super cool group of pollinators, providing resources for them and their hosts (see this and this post to learn some ways to do this) is key to maintaining the populations of these rare and fascinating parasitic bees!

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

My flowers should be attracting lots of pollinators, but they’re not. What’s going on?

September 2, 2021Maryland Grows2 Comments

The presence of pollinators on flowers depends on many factors, so it is hard to know exactly why they are not visiting your flowers as much as you would expect. Plus, sometimes these factors happen simultaneously, so it may be that it is not one but the combination of factors that leads to the lower floral visits one sees. In today’s post I would like to touch on some potential reasons of why flowers may not be visited, and what we all can do to change it!

Are there really no pollinators?

We tend to think of pollinators as honeybees, and if we don’t see them we think that there are no pollinators. Pollinators come in a huge variety of types (see here to learn more!), and although you may not be attracting a lot of honeybees, you may be doing great at sustaining other pollinators!

To test if this is what is happening in your flower patch, observe carefully the flowers to see if there are other insects visiting them. Those may be pollinators too! Indeed, small wild bees, syrphids, and small beetles visit flowers often, but are usually inconspicuous. Also, make sure that you are observing your flowers when pollinators are most active, which tends to be under sunny and warm weather conditions.

Some pollinators are tiny and inconspicuous. Although seemingly not being visited, the flowers on this picture are visited by several beetles and bees. Can you see them? Photo: A. Espíndola

Pollinators have not yet had time to find your flowers

Especially if your flower patch is in an area or neighborhood where there aren’t many flowers, the pollinators in your area will need a bit of time to know that the flowers are there! It’s like when a new shop opens and it takes a while for people to know it exists. If you continue to have flowers there over the season and years, pollinators are going to start coming more regularly and you should see an increase over time.

Not sufficient(ly diverse) flowers

If you indeed live in a region where there are not many floral resources available for pollinators, you can plant more (diverse) flowers next year and/or talk to your neighbors and have them plant flowers too! The more flowers in a region/neighborhood, the more pollinators you may end up attracting overall! On this, consider talking to your City leadership and inquire on whether they would be interested in supporting pollinators by becoming a certified Bee City USA city.

Flower beds and gardens with many plant species are ideal to increase the number of pollinators in our green spaces. Photo: J. Dean

Lots of flowers but not many places to nest

Even though most pollinators can fly to get to floral resources, their flight ability depends on the species. Some species can fly some miles, while others forage just close to their nests. To make sure that there is a lot of pollinator diversity in your flower patch, you can create conditions that favor the nesting of those species that can’t travel far. For this, a great thing to do is create nest-friendly spaces on your property. One can also establish practices that ensure that critical pollinator developmental stages (e.g., overwintering stages, larval development) also have sufficient resources. This can be done, for instance, by leaving leaf litter on the ground over winter and protecting overwintering spaces (check this other post to learn more).

Some pollinators are territorial

Some pollinators (e.g., some bumblebees, honeybees, large carpenter bees, wool carder bees) can “push out” other smaller pollinators, especially while the males are looking for a mate. If the large ones are very abundant, it could be possible that they are chasing away the small ones. This would not explain an absolute lack of pollinators, but would be able to explain certain drops in abundances at certain times of the year.

Pesticide drift

Pesticide drift is a big problem for the protection of beneficial arthropods, and can lead to pollinator (and other beneficial insects) death. Drift happens when a region in the vicinity of your property is treated with pesticides, and the products drift into your property. This is really problematic when the applications are done at the wrong times, with the wrong concentrations, or using the wrong means. In particular, this can be a problem when homeowners decide to perform whole-yard spraying to control mosquitoes, which is not recommended (an exception to this are controlled community-wide sprays occasionally done by the State Department of Agriculture if disease spread –e.g., West Nile Virus — is a concern).

Unless there are strong reasons for pesticides to be continuously applied in the vicinity of your property (e.g., major and sustained outbreak of mosquito populations), this is normally restrained in time. If there has been drift, you would be seeing a drop in pollinators compared to a previous time in the year (say, the week prior to the potential drift event). If drift has actually happened, but is not happening anymore, one would expect to see the populations of your pollinators increase with time, since new pollinators could be attracted from other surrounding areas. If you suspect that drift is an issue, you can discuss with your neighbors and see if the applications are really necessary, if they are done at the proper times (ideally in the night or when beneficial insects are not active) and/or get them in touch with your UMD Extension officers, who can recommend whether treatment is even needed, and if so, how to do it. You can send your question online to Ask Extension.

If not properly done, pesticide applications can lead to pesticide drift to neighboring areas and pesticide runoff to our watersheds. Always carefully read the labels appearing on pesticide containers, and consult your Extension agents if you want to make sure to do a safe application. Image: C. Rusconi

Just a less-active year

If you have been successful in the past, it could just be that this year there is just a smaller population of pollinators in the area when your flowers are growing. For example, maybe the warm winter did not help some pollinators properly overwinter, or some disease outbreak locally affected pollinators in your area. If next year you realize that this was indeed a one-year thing, this will then be easily explained by natural fluctuations in pollinator populations.

Think broadly and don’t give up!

Remember that sometimes it is not one but the combined effect of these factors that makes that pollinator abundances drop in our gardens. If you’re not sure what the actual reason may be, your best call is trying to implement as many of the actions as you can, so at least you can exclude some variables. Either way, remember that your actions are likely not going to bring results from one day to the next, but rather from one season to the next! For example, many pollinators reproduce only once per year, so you may have to wait until the next generation (the following year) to see a difference. So, don’t give up if you don’t see an effect right away! You’re likely doing the right thing; you just need to wait a bit longer to see the result!

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