Attention all gardeners: how much do you know about the insects that inhabit your landscape? Can you tell which ones are beneficial and which are potentially damaging? Insects are considered the largest biomass of all terrestrial animals and with 10 quintillions (10,000,000,000,000,000,000) alive at any one time, it's good to know that only between 1 and 3 percent are considered pests.
As to the other 97-99%, many “bugs” are actually very helpful. Some of them keep other pests in check by dint of their spot on the food chain. Others, such as our native bees, honeybees, butterflies, moths and others help to fertilize our food and flower-producing plants by spreading pollen.
In the natural world, there are truly no “good” or “bad” bugs, but as gardeners, our goal is often to protect crops and ornamental plants from insect damage. To that end, UC Master Gardeners practice Integrated Pest Management (IPM), a holistic long-term strategy that employs biological control, habitat manipulation, modification of cultural practices, and the use of resistant varieties instead of reliance on pesticides and other means of chemical control.
A key component of IPM is the use of “Natural Enemies,” which are defined scientifically as organisms that kill, inhibit reproduction or otherwise reduce the numbers of other organisms. In other words, “Natural Enemies” act as our allies by controlling the less desirable bugs that do damage to our gardens and crops.
Here are some examples of “Natural Enemies” and what they do:
- Predators: spiders, many beetles, flies, true bugs, lacewings and other bugs who make their living by eating other insects.
- Parasitizing insects: while it may sound like a sci-fi movie, parasitic insects, such as small wasps, lay their eggs inside other insects or their eggs. Also called “Parasitoids,” these insects can make a dramatic reduction in the numbers of undesirable insects.
- Insect-eating animals such as birds, bats, amphibians and certain reptiles are also considered “Natural Enemies.”
Once you get to know the “Natural Enemies” in your garden, you'll also want to learn how to recognize their different life stages. This is important to know because they eat different things at different life stages. For instance, only the larval forms of insect
predators such as lady beetles, hoverflies, lacewings, and parasitic wasps consume pests whereas the adult forms feed primarily on nectar or pollen.
Garden stores often sell certain types of beneficial insects but you can recruit your own and keep them in your garden by creating conditions that support their complete life cycle. Such a garden is often called an “insectary.” Here are ways to create an insect-friendly habitat in your garden:
- Plant a combination of perennials and annuals for greater insect diversity.
- Grow plants of varying heights in both sun and shade to provide food and habitat for different insects and life stages–eggs, pupae, larvae, and adults.
- Make sure to include plenty of plants with small or compound flowers such as asters, alyssum, small sunflowers, yarrow, cosmos, mints, basil, thyme, lavender, parsley, dill, borage, and other herbs--a majority of beneficial insects prefer them.
- Remember that the unwanted pest in your garden is food for your natural predator friends. You may need to accept some level of plant damage to sustain your allies.
- Use chemical pesticides only as a last resort and seek out less toxic alternatives. Too often, beneficial insects are killed just as effectively as the pest species and can make a problem worse.
At the end of the day, we all want beautiful, thriving gardens. By focusing on providing proper nutrients and water and creating a welcome home for our insect allies, we can create healthy, resilient plants that will survive any insect invasion.
- UC IPM Natural Enemies Gallery
- UC IPM Pest Notes, Biological Control and Natural Enemies of Invertebrates
- How to Attract and Maintain Pollinators in Your Garden
- Less Toxic Insecticides
This article was written by Master Gardener Jamie M.Chan and edited by Master Gardeners Maggie Mah and Cynthia Nations.