Lending Insects a Helping Hand in our Gardens

By Laura Gardner, Master Gardener in Training

When some of us think of insects, it is common for them to be thought of in a negative light. Some of our earliest childhood memories include being stung, bitten, or just plain scared by the sight of them. I can remember running screaming from an outhouse at a provincial park when I was about five years old. What was so scary? It was the sight of a Yellow Garden Spider (Argiope aurantia) hanging in its web in the stall. Fortunately, the experience didn’t make me fear or dislike spiders and as a gardener I know how beneficial they are to have around. While some insects certainly do deserve our scorn— invasive species such as the LDD moth (Lymantria dispar dispar); Emerald Ash Borer (Agrilus planipennis); Japanese Beetle (Popillia japonica), etc.—by and large, the majority of insects are harmless and beneficial. Not long ago, I saw a couple—perhaps grandparents, out for a walk with their grandson. One of them was urging the young boy to stomp on an ant on the pavement, calling out “Get it! Get it!” It was disheartening to see. It is experiences like this that call for a shift in our thinking about insects.

Bumblebee (Bombus sp.) on False Sunflower (Heliopsis helianthoides)

I recently got a sneak preview of a book by British entomologist Dave Goulson called Silent Earth: Averting the Insect Apocalypse (Harper Collins). It is to be published this Fall (September 2021). The copy I reviewed was an e-book proof and so page numbers referred to here may change in the final published copy. Goulson’s work is primarily focused on bumblebees and as the founder of the Bumblebee Conservation Trust in the UK, he is dedicated to reversing the decline of them. He is also known for his work that was instrumental in influencing the European Union’s decision to ban neonicotinoids in 2013. Goulson wrote this book in an effort to bring more public attention to the recent and rapid decline of global insect populations—which are critical for our planet’s survival. He also explores the chief causes of insect declines such as habitat fragmentation, industrial farming practices, pesticides, climate change, and non-native insect diseases (p. 71) and provides suggestions for readers that can help support insects—especially gardeners.

Bumblebee (Bombus sp.) on Sweet Joe Pye Weed (Eutrochium purpureum)

Here are a few highlights from the book:

Goulson refers to a phenomenon called “Shifting Baseline Syndrome” where humans tend to only see their current world as “normal” and are unable to detect changes over time. Humans also tend to have something called “personal amnesia” in which they downplay the extent of change (p. 64-65). With these points in mind, it is no wonder that most people would not know that insect populations have recently declined by as much as 75% (p. 50) and that there have been parallel declines in populations of insectivorous birds (p. 58). One bird that I remember as a child that I haven’t seen since is the Eastern Meadowlark (Sturnella magna). This species is one of those that depends on insects in its diet.

One concern that the author has is the level of human awareness of the existence of the natural world. It is important to learn the names of plants and animals—otherwise they cease to exist. If they don’t exist, their importance can’t be recognized. Astonishingly, in 2007, some of the words eliminated from the Oxford Junior Dictionary included words such as acorn, fern, moss, clover, kingfisher, otter, among others (p. 225).

87% of all plant species require pollination in order to flower, produce fruit/seeds, and ensure perpetuation of the species. This includes 75% of all agricultural crops (p. 26). Most of this is performed by insects and a large part is performed by those other than bees—flies, ants, beetles, wasps, moths and butterflies. A world without insects means that we would need to subsist mainly on cereal crops as these can be wind-pollinated. I can’t imagine going without fruits such as strawberries, apples, cherries, raspberries, and even my morning coffee (p. 26).

Insects are not only important pollinators, but they assist in the development of healthy soils. Not only do they help to aerate soil, they are valuable decomposers of organic matter—participating in a process along with bacteria that help make nutrients more available to plants (p. 29, 31).  As biological control agents, predatory insects such as Lady Bugs (Coccinellidae spp.), Lacewings (Chrysopidae spp.), Ground Beetles (Carabidae spp.), Wasps (Vespidae spp.), etc., can help us reduce the need for pesticides.

Blue Mud Dauber (Chalybion californicum) on Swamp Milkweed (Syriaca incarnata)

What can we do to help?

Despite the current state, Goulson is optimistic that insect declines can be stabilized or reversed because they are generally good at reproducing—we just need to support them better (p. 216). Here are some ideas:

  1. Learn how to identify the difference between harmful and beneficial insects. The majority (95%) are the latter.
  2. Reduce or avoid the use of pesticides and give beneficial predatory insects a chance to take care of the problem first (p. 277). Even so-called organic treatments such as diatomaceous earth, BTK, horticultural oils, etc. need thoughtful consideration before use as they can harm harmful as well as beneficial insects.
  3. Learn how to differentiate between irreversible and cosmetic damage in your plants. Accept that plants are meant to be food sources for insects and some imperfections and damage is ok. Give up growing ornamental plants that are persistently defoliated by certain insects (e.g. Asiatic Lilies).
  4. Incorporate a wide range of native plants that flower throughout the season in your garden to attract beneficial insects. One of the best late flowering perennials is New England Aster (Symphyotrychum novae-angliae). It provides a valued food source for migrating Monarch butterflies. Some of the best food sources for insects are early flowering trees such as Serviceberry (Amelanchier spp.), Maple (Acer spp.), and Crabapple (Malus spp.).
  5. When using mulch in flower beds, leave some soil exposed so that ground nesting bees can have easy access. Some solitary wasps such as Mud Daubers (Sphecidae spp.) also need easy access to bare soil in order to glean material to build their nests.
  6. Reduce lawn and use the space for more plants. Reduce mowing of the lawn that exists. Allow a corner of your garden to “grow wild” and “get messy.”  (p. 277).
  7. Choose native plants over “nativars.” A nativar is a cultivated variation of a native plant. Some are supportive of pollinators but many are sterile or lack pollen and therefore are unable to provide food. The ones that are most likely to be the least supportive will have features such as double blooms, different leaf colours, etc. Reduce planting of ornamental annuals like Petunias, Begonias, Pansies, etc. because of their tendency to have no pollen or nectar (p. 233). That being said, some of these plants can still be enjoyed.
  8. Choose a range of plants that support the broadest number of insect species. While Milkweeds (Asclepias spp.) are in the limelight as being supportive of Monarch Butterflies (Danaus plexippus), compared to some other plants, they only support 12 Butterfly and Moth species (Tallamy, Bringing Nature Home). Goldenrods (Solidago spp) support 115 different species. Some, like Canada Goldenrod (Solidago canadensis) can be aggressive in small gardens but there are more restrained types such as Blue-Stemmed Goldenrod (Solidago caesia), and Zigzag Goldenrod (Solidago flexicaulis).
  9. Avoid aggressive fall and spring clean-up of leaves and hollow, dead stems. Doug Tallamy describes the practice of waiting 7-10 consecutive days of 10 degree C. temperatures for insects to emerge as myth as many insects emerge at different periods throughout the season. For example, Io (Automeris io) and Luna Moth (Actius luna) emerge around mid May (Tallamy, Leaf Litter: Love it and Leave it).
  10. Recognize that commercially produced “Bee Hotels” can become populated by non-native bees such as European Orchard Bee (Osmia cornuta), Horned-Face Bee (Osmia cornifrons), and Blue Mason Bee (Osmia coerulescens) as well as native bees (p. 135). If used, periodically clean them so as to reduce mites and fungi that can be harmful to the bees.
  11. Reconsider taking up beekeeping as a hobby. The European Honey Bee (Apis mellifera) threatens native bees because they take the lion’s share of available plant pollen (p. 139). It is also not a good strategy to rely on one species for pollination in case something happens to that species (p. 33).
  12. Raise awareness and share your knowledge with family and friends. You can convince others that insects need our help if they realize they themselves will be personally impacted by their decline (p. 216).

Selected Resources

Holm, Heather. Pollinators of Native Plants: Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants (Pollination Press, 2014).

Tallamy, Doug. Bringing Nature Home: How you can Sustain Wildlife with Native Plants (Timber Press, 2009).

Tallamy, Doug. Leaf Litter: Love it and Leave it. April 2021. Online: https://tinyurl.com/4jphhnbc

Walliser, Jessica. Attracting Beneficial Bugs to your Garden: a Natural Approach to Pest Control (Timber Press, 2013).

Xerces Society for Invertebrate Conservation. Visit https://xerces.org/publications to view and download a wide range of factsheets and other guidance documents concerning beneficial insects, native plant lists, pesticides, habitat construction, and more.

Monarch Butterfly Caterpillar (Danaus plexippus) on Swamp Milkweed (Syriaca incarnata)

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