By Mary Free, Extension Master Gardener
Thirteen years ago the United States Senate designated a week in June as National Pollinator Week “recognizing the importance of pollinators to ecosystem health and agriculture in the United States and the value of partnership efforts to increase awareness about pollinators and support … ” Join the Master Gardeners of Northern Virginia in observing this week, June 22–28, 2020, by learning more about some of the insects, birds, bats and other small mammals that pollinate at least 80 percent of our flowering plants and about 33 percent of our food crops as well as what you can do to sustain pollinators.
Each Tuesday we introduce a native “mystery plant” on Facebook. This week we have chosen one that feeds a wide variety of pollinators and other insects, unlike many of the cultivars and nonnative plants of this genus commonly used as foundation plants in Northern Virginia. Of course, if we revealed its identity today, it would not be a mystery, so please visit us tomorrow on Facebook to see if you can guess what it is. (We have already provided a hint.)
Pollinators play a critical role in producing an affordable food supply and healthy ecosystem and yet insect and bird populations have continued to decline, mostly due to human agricultural and development activities. A 2019 study, Worldwide decline of the entomofauna: A review of its drivers found that 40 percent of insect species are threatened with extinction with the most vulnerable species being Hymenoptera (primarily wild and honey bees) at 44 percent and Lepidoptera (butterflies and moths) and Coleoptera (especially dung beetles) at 34 percent each. Besides habitat loss due to agriculture and urbanization, other factors that contribute to decline include chemical use, pollution, invasive species, disease, and climate change.
The US lags behind other agricultural nations (i.e., the European Union, China, and Brazil) in banning pesticides harmful to humans and surrounding ecosystems. According to a 2012 EPA study, 66 percent of user expenditures on conventional pesticides in the US was by the agriculture sector. The home and garden sector spent 24 percent, primarily on insecticides. EPA estimated that 88 million US households used pesticides.
Knowing the dangers posed by pesticides, including insecticides, herbicides, fungicides, and repellents, we have written a mosquito and tick control series on how to protect yourself without using noxious chemicals, thereby protecting pollinators too. The first two articles, Protecting Yourself From Mosquitoes . . . Without Harming Pollinators and Protecting Yourself From Ticks . . . Without Harming Pollinators were posted earlier this year. The third in the series is Pollinators Under Threat and How You Can Help. On Wednesday, we will feature Part 1. Threats to Pollinators, describing harmful urban landscape practices, which in addition to pesticide use, include overuse of nonnative plants, grass monocultures, impermeable surfaces, and night lights.
As urban areas continue to grow, it is vital to understand how urbanization is driving pollinator diversity and pollination. Although urban sprawl into wild lands negatively affects pollinator diversity, when lands with intensive farming were urbanized (with less than 50% impervious surface) and no longer subjected to high levels of pesticides, pollinator diversity actually increased. Further, diversity “generally increased with the amount of urban green spaces at the landscape scale, and locally with availability of nesting resources and flowering plants.” (Wenzel, January 2020). Of course green spaces devoted to parkland and tree canopy (especially important for early season pollinators) are more beneficial than golf courses and lawns. Whether you have a balcony or acres of land, you can make a difference by Creating Inviting Habitats for pollinators with a succession of blooms spring through fall as well as places where they can water and shelter. On Thursday, read Pollinators Under Threat and How You Can Help, Part 2. Creating an Oasis for Pollinators to learn more.
Some very bad news: the annual eastern monarch butterfly count released in March 2020 reported a 53 percent plunge from the previous year, mostly due to bad weather during the spring and fall migrations on top of more breeding habitat loss in the US. Overwintering monarchs occupied just 7 acres of land, well below the extinction threshold of 15 acres! Although the western monarch population remained stable last year, it suffered a dramatic decline from 200,000 butterflies in 2017 to only 30,000 in 2018. Researchers attributed that decline to habitat loss, pesticide use, and climate change although some speculated increased planting of tropical milkweed (Asclepias curassavica) might also be a contributor.
Milkweed is the host plant for monarch butterflies. Unlike native milkweeds, tropical milkweeds bloom late into the season. It is a topic of debate whether this confuses monarchs into breeding when they should be migrating or overwintering. Additionally in mild climates where this tropical milkweed does not die back, a monarch butterfly parasite, Ophryocystis elektroscirrha (aka OE) can remain on the leaves to be ingested by succeeding generations of caterpillars, in turn infecting and weakening adults. One potential solution is to cut tropical milkweed to the ground in the fall.
The other solution is to choose only native milkweed species, like Asclepias incarnata (swamp milkweed) or our weekly featured Tried and True Native Plant Selection for the Mid-Atlantic, Asclepias tuberosa (butterfly-weed), for your garden. Remember to site the milkweed where you will not mind a plant defoliated by hungry monarch caterpillars. Also refrain from pesticide use near the milkweed or any other pollinator plants.
This Friday, our milkweed fact sheet will be supplemented by a video. The accompanying article, The Perils of Pollinia and More About Milkweed, will discuss the challenges insects face when they try to obtain nectar from milkweed plants as well as a comparison of three different native milkweed species.
Planting the right plants in the right places will increase the visits of specific wildlife to a garden. To create a monarch habitat plant native milkweed plants (Asclepias spp.) that provide food for monarch caterpillars, as well as nectar plants to feed adult butterflies. To attract hummingbirds plant a succession of red bloomers: Aquilegia canadensis (wild columbine) for spring, Lonicera sempervirens (trumpet honeysuckle) for late spring and intermittently into fall, Monarda didyma (scarlet beebalm) for early summer, and Lobelia cardinalis (cardinal flower) for late summer. A butterfly garden should include Solidago spp. (goldenrod) and asters, which attract the highest numbers of Lepidoptera, 114 and 106 species, respectively, according to Doug Tallamy. Asters, also, along with sunflowers (Helianthus spp.) and coneflowers (Echinacea and Rudbeckia), rank among the top choices for seed-lovers like songbirds. But for sheer numbers and diversity of pollinators during a blooming season, Pycnanthemum muticum (short-toothed mountain-mint) is difficult to beat.
A three-year Penn State Extension study ranked native Pycnanthemum muticum #1 for pollinator visits and # 2 for pollinator diversity. Last year, myriad insects were active on the mountain-mint in my garden for almost three months and I observed several species that were new to me including the tiny Hylaeus bee, which will be featured on Saturday in an article and video, BEE-havior: The Bubble Bee – Hylaeus.
On Sunday, we will end our Pollinator Week celebration with another BEE-havior video entitled Bee Bottoms and Turtleheads. For now, we’ll leave that subject to your imagination.
Meanwhile, I’ll be out in the garden searching for pollinators to photograph. Connect with nature yourself by strolling through a garden. Before you stop to smell the roses, though, see what’s pollinating them (and other flowers) first, especially if you don’t want a bee stinging your nose! Although late June may not be the best time for planting, it’s never too early to consider what pollinator-friendly natives – see our Best Bets to Attract Pollinators–to add to your property to create an oasis for pollinators, a Monarch Waystation or Wildlife Sanctuary come fall.
- Atwood, D. & Paisley-Jones, C. Pesticides Industry Sales and Usage, 2008-2012 Market Estimates. United States Environmental Protection Agency.
- Audubon At Home. Audubon Society Northern Virginia.
- Bees, Bugs & Blooms – A pollinator trial. Penn State College of Agricultural Sciences. (2019).
- Best Bets to Attract Pollinators. Master Gardeners of Northern Virginia.
- Cameron, L. A. Protecting Yourself from Mosquitoes…Without Harming Pollinators. Master Gardeners of Northern Virginia. (2019).
- Daley, J. How This Popular Garden Plant May Spread Parasites That Harm Monarchs. Smithsonian Magazine. (2018).
- Donley, N. The USA lags behind other agricultural nations in banning harmful pesticides. Environmental Health 18, 44 (2019). https://doi.org/10.1186/s12940-019-0488-0
- Eastern Monarch Butterfly Population Plunges by More Than Half. Center for Biological Diversity. (2020).
- Free, M. Creating Inviting Habitats: For the Birds, Butterflies & Hummingbirds. Virginia Cooperative Extension. (2013).
- MacPhail, V.J., Richardson, L.L. & Colla, S.R. Incorporating citizen science, museum specimens, and field work into the assessment of extinction risk of the American Bumble bee (Bombus pensylvanicus De Beer 1773) in Canada. J Insect Conserv 23, 597–611 (2019). https://doi.org/10.1007/s10841-019-00152-y.
- McIntyre, J. Protecting Yourself from Ticks…Without Harming Pollinators. Master Gardeners of Northern Virginia. (2019).
- Monarch Waystation Program. Monarch Watch.
- Sánchez-Bayo, F. & Wyckhuys, K.A.G. Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation, Volume 232, 8–27 (2019). https://doi.org/10.1016/j.biocon.2019.01.020
- Tallamy, D. Bringing Nature Home. (2018)
- Top 10 Plants to Attract Songbirds. National Geographic. (2017).
- Tried and True Native Plant Selections for the Mid-Atlantic. Master Gardeners of Northern Virginia.
- Wenzel, A., Grass, I., Belavadi, V.V. & Tscharntke, T. How urbanization is driving pollinator diversity and pollination – A systematic review. Biological Conservation, Volume 241 (2020). https://doi.org/10.1016/j.biocon.2019.108321
- Weintraub, K. What’s happening to the monarch butterfly population? The New York Times. (2020).