In any well-balanced ecosystem, there are pests and there are natural enemies, or beneficial insects. For this reason, some pests must be present in the environment for the beneficial insects to survive. In a garden, a pest is an insect that feeds on or transmits disease to desired plants, whereas beneficial insects maintain the ecosystem balance by consuming these pests.
3 Types of Beneficial Insects
Pollinators: Not only do many bee and fly species pollinate plants, they also eat and/or destroy many “bad bugs” in the landscape.
Predators: Some insects are predaceous in their larval stage, while others are as adults. Some are even predaceous as both larvae and adults. Additionally, some predators have a diverse diet, while others eat only one type of food source (ladybugs eat aphids).
Parasitoids: These are insects that live on or in a host insect so they can feed on it, usually killing it in the process. Many are parasitic fly or wasp species that inject their eggs into the host. The eggs hatch, then transform into larvae, and because they’re within the host insect, they have a natural food source immediately available.
How to Attract Beneficial Insects to Your Garden
Create a diverse environment in your landscape—it’s that simple! But, what does that mean exactly? A diverse garden is one planted with a mixture of plants, having varied bloom time, flower shape, and size all inter-planted with one another. An example would be planting vegetables and companion flowers such as marigolds, cosmos, and nasturtium. Did you know that planting garlic with peas, lettuce, and celery will help keep aphids away from your crop?
All beneficial insects require a reliable food source, and for some of them, it is specific. When creating your palette, remember our beautiful native plants—many wonderful bugs depend on them! The following is a sample list of insectary plants that specifically attract and keep beneficial insects in the garden.
FLOWERS, VEGETABLES & HERBS
- Sweet alyssum – Lobularia maritima
- Parsley – Petroselinum crispum
- Lupine – Lupinus spp.
- Oregano – Origanum vulgare
- Sunflower – Helianthus annuus
- Lavender – Lavendula spp.
- Yarrow – Achillea spp.
- Fennel – Foeniculum vulgare
- Coreopsis – Coreopsis spp.
- Dill – Anethum graveolens
- Cosmos – Cosmos bipinnatus
- Sage – Salvia spp.
- Candytuft – Iberis umbellate
- Lovage – Levisticum officianle
- Goldenrod – Solidago altissima
- Lemon balm – Melissa offocinale
- Marigold – Tagetes spp.
- Thyme – Thymus spp.
- Flowering Sage – Salvia
- Chamomile – Chamaemelum nobile
- Dianthus – Dianthus spp.
- Broccoli – Brassica oleracea
- Lilyturf – Lirope spicata
- Carrot – Daucus carota sativus
- Phlox – Phlox spp.
- Blazing Star or Gayfeather – Liatris spp.
- Zinnia – Zinnia spp.
- Daisy – Belllis perennis and Leucanthemum spp.
- Statice – Limonium spp.
- Angelica – Angelica spp.
*Planting fruit trees, raspberries, and brambling plants provides wonderful habitat/food supply.
PACIFIC NORTHWEST NATIVE PLANTS
- Buttertfly Weed – Ascelpias species
- Evergreen Huckleberry – Vaccinium ovatum
- Bugleweed – Ajuga reptans
- Larkspur – Delphium
- Wallflower – Erysimum linifolium
- Madrone – Arbutus menziesii
- Pincushion Flower – Scabiosa columbaria
- Oregon Grape – Mahonia aquifolium
- Joe Pye Weed – Eupatorium purpureum
- Red Twig Dogwood – Cornus sericea
- Stonecrop – Sedum
- Snowberry – Symphoricarpos alba
- Gaultheria shallon – Salal
- Red Flowering Currant – Ribes sanguinium
- Elderberry – Sambucus
Pollinator Syndromes
Bees: Prefer flowers colored bright white, yellow, blue/purple (bees can’t see red); best flower shape is shallow and tubular with a landing platform
Bats: Prefer flowers colored dull white, green, or purple with a strong musty fragrance at night; best flower shape is regular or bowl shaped and is closed during the day
Butterflies: Prefer flowers in bright colors including red and purple; best shape is a narrow tube with a spur or a wide landing pad
Hummingbirds: Prefer flowers in scarlet, orange, red, or white with tubular shapes, large funnel, or cup shapes; perch support is added bonus
Moths: Prefer pale-colored flowers in dull red, purple, pink, or white with a regular or tubular shape; strong sweet fragrance at night is especially attractive
Protecting Beneficial Insects in Your Garden
Because most insecticides are “broad spectrum,” meaning they kill a wide variety of insects, beneficial insects are extremely vulnerable. Should you decide to use insecticides in your home landscape, great precaution must be taken to protect beneficial insect populations:
- Whether natural or chemical-based, choose the least toxic product available for the situation
- Spray only the area(s) on the plant that are affected
- Spray when many insects are less active—dawn or very early morning
- Do not spray plants that are in bloom!
In summary, once you choose to use beneficial insects in your garden, protect their survival by not using insecticides unless absolutely necessary. Call or visit your local Dennis’ 7 Dees Garden Center—knowledgeable staff may have alternative suggestions for you!
Beneficial Bug Resources
- Good Bug, Bad Bug book by Jessica Walliser
- The Great Sunflower Project
- Oregon State Extension Services (many articles available for this subject)
- WSU Clark County Extension (another wonderful resource)
- Xerces Society