By Valorie Shatynski
November 2023

Most of us enjoy the sight of a butterfly flitting and lilting from blossom to blossom in our garden, but what about those less glamorous insects and other garden critters?   Why should we not only tolerate spiders, pill bugs, aphids, bees or termites, but encourage them?   

First, why are insects important (think “beneficial”) to us and the planet?   Every insect has a critical job to perform in our ecosystems, right down to our own neighborhoods and yards.  For example, the sight of hummingbirds in our yards is a delight.  Did you know that 80% of their diet includes ants, aphids, fruit flies, gnats, weevils, beetles, mites and mosquitoes, spiders and insects trapped in spider webs?   These “bad bugs” are essential food sources for the hummers!  If we wipe out those pesky critters, what happens to our hummingbirds?

A May 2020 National Geographic article provides a clearer picture of beneficial critter functions in five key categories:

1. Providers:  The hummingbird diet highlights how insects and other garden critters support almost every other animal on the planet – birds, reptiles, amphibians, and fish; even some human populations rely upon insects as a source of protein in their diets.
2. Decomposers: These are insects (dung beetle) and other organisms (worms, sow bugs), that eat what humans consider waste – manure, dead animals, and plants, and their “output” is nutrient-rich soil enhancing matter!
3. Pest Controllers: Many insects are predators that can manage populations of destructive insects in our gardens and agricultural crops.  A few of these predators are ladybugs, damsel bugs, wasps, and hover flies.  The hover fly looks like a little bee, but it is actually a Syrphid Fly, whose larvae can eat up to 400 aphids, according to Cornell University College of Ag and Life Sciences. Cornell has an excellent list of insects and critters that can be used in our gardens rather than pesticides:  https://biocontrol.entomology.cornell.edu/ag.php
4. Pollinators: According to the Xerces Society, see: https://www.xerces.org/pollinator-conservation/about-pollinators , in addition to bees and butterflies, insect pollinators include wasps, flies and beetles.  In fact, there are over 85,000 species of flies worldwide - very heavy lifters as pollinators.
5. Soil Engineers:  Insects and other critters in this category include termites, ants and worms, which tunnel in all types of soils. This tunneling aerates hard soil and allows it to hold water.  These organisms also add nutrients which allow humans to use the soil to raise crops and create thriving landscapes.

Understanding the multitude of benefits insects provide, what can we do to attract and support them in our landscapes and gardens?  Our first challenge is to reconsider the idea of the “bad” versus “good” bug. How do we control the “bad” bugs that can cause damage in our gardens without wiping out insects and organisms that we need and want by overuse of pesticides.

Scientific research for agriculture and landscape management has resulted in the concept of Integrated Pest Management (IPM).  The University of California defines IPM as “…a strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and non-target organisms, and the environment.” https://ipm.ucanr.edu/what-is-ipm/

The key to managing pests in your garden is to properly identify and then monitor the “pest” and determine if the damage can be tolerated or reduced.  The San Diego Master Gardner Hotline often receives inquiries from residents that have tried a pesticide or home remedy which has not had an impact on the target pest.  Upon investigation, the pest has been mis-identified and an incorrect pesticide/remedy had been applied.  In many cases, an approach not even needing a pesticide is more effective.  For example, a sharp blast of water in intervals of 3-4 days is the solution to an aphid infestation on plants. Our Master Gardener Hotline is available via email (please attach photographs to help us see what you are seeing), or by calling our Hotline phone 24/7 to leave a message. One of our volunteers will call you back to troubleshoot your issue.

Another strategy we can pursue to support native insects is to introduce locally native plants into our landscapes and gardens. Native plant experts acknowledge that many gardeners want to keep their non-native gardens intact, and have demonstrated that integrating select natives into the mix can be aesthetically pleasing while supporting native bees, spiders, and other organisms. A hard look at pesticides reveals that nearly all are used against non-native insects that feed on non-native garden plants. A native garden, or one with some natives present, reduces the need for pesticides.   

Adding local native plants to your garden is a matter of determining the soil and regional/microclimate where you live.  The next step is to select native plants that will have the same needs (water, sun, shade, soil type, etc.).  It is important to make sure all the plants are grouped together by watering zone.  The online database CalScape at https://www.calscape.org/ allows you to enter your home address, and search for plants ideal for your location.  The database offers categories by plant type such as trees, shrubs, etc., and by plant-need such as sun, shade, damp soil, easy to grow, etc.   Best of all, the CalScape website has a Garden Planner Tool.  Enter your zip code and answer 4 questions to get started.   https://gardenplanner.calscape.org/

A few carefully selected locally native plants will draw native insects that “specialize” in those plants, as well as benefit soil organisms that do their work “under the radar” unnoticed in our gardens. An example of insect/plant specialization is the Monarch butterfly and milkweed. 

Whether our goal is to improve crop production, reduce pests that attack our aesthetic landscape, or reduce water use, pest management and use of native plants are two very effective strategies. Over time, you will see evidence that the insects and the other organisms in your gardens will regain their natural balance.  Happy Gardening!

References:

Hummingbirds: UCANR Bug Squad post “What You May Not Know About Hummingbirds,”
https://ucanr.edu/b/~8h7

Regional Entomology at the San Diego Natural History Museum:
https://www.sdnat.org/science/entomology/

Insects in Green Spaces – The Royal Entomology Society (this free download provides ideas to promote insects, types of insects with excellent descriptions and photographs)
https://www.royensoc.co.uk/shop/publications/insects-in-green-spaces/

UCANR Integrated Pest Management
https://ipm.ucanr.edu/PMG/menu.homegarden.html

Cornell University Biological pest control – The Syrphid Fly
https://biocontrol.entomology.cornell.edu/predators/syrphids.php

The California Native Plant Society (CNPS) has online Native Gardening Resources at
https://www.cnpssd.org/garden-resources

The CNPS Native Plant Profile database is:
https://www.cnpssd.org/plantprofiles