Why Your Garden Needs Beneficial Insects
by Cindy King, CPH, The Mill of Kingstown
Let's talk about how we can attract beneficial insects to our gardens to help control aphids, caterpillars, thrips, soft-bodied scale, and insect eggs, and to assist in limiting pesticide usage.
Beneficial insects will pollinate, collect nectar, and feast on insect eggs, pupae, and adults. They prefer composite flowers in yellow, purple, blue, and pink. Plants in the following families—Apiaceae (Carrot family), Asteraceae (Aster family), and Verbenaceae (Verbena family)—provide food and habitats for beneficial insects.
By planting groups of plants from these families sporadically in your garden, you can limit pest populations.
Plants in the Carrot family include
- Cilantro
- Dill
- Fennel
- Queen Anne’s lace
These are known for attracting soldier beetles, lady beetles, praying mantids, lacewings, syrphid flies, and other beneficial insects. These beneficial insects help keep pests in check.
Another plant family, the Asteraceae, includes
- Gaillardia
- Echinacea
- Coreopsis
- Cosmos
- Solidago
- Marigolds
- Helianthus
- Yarrow
These plants not only attract beneficial insects but also pollinators that help pollinate vegetables and fruits, ensuring the best harvest possible. Solidago is one of the best plants for attracting both beneficial insects and providing pollen and nectar to bees. Once established, this plant is drought-tolerant, resistant to deer and rabbits, and, depending on the variety, can grow in sun to shade.
- Verbena bonariensis
- Lantana
- Verbena hybrids
These also attract pollinators and provide excellent hunting grounds for beneficial insects. These plants tolerate full sun and drought conditions.
If you are planting a flower garden, incorporate these plants into your design. You will notice that the plants in the garden will not suffer from severe pest infestations during the summer months. Use them around your vegetable garden to limit infestations of caterpillars and other pests.
When using beneficial plants, realize that the beneficial insect population increases when the pest population reaches a threshold that allows beneficial insects to complete their life cycle. You will have some damage to plants as the pest population builds up, but the beneficial insect population will help reduce it to a very manageable number.
Beneficial insects that can help control common garden pests:
| Beneficial Insect | Common Prey | Additional Notes |
|---|---|---|
| Ladybug (Coccinellidae) | Aphids, scales, mites, whiteflies | Both adults and larvae are voracious predators. |
| Lacewing (Chrysopidae) | Aphids, whiteflies, mites, mealybugs | Especially effective in the larval stage for controlling soft-bodied pests. |
| Hoverfly (Syrphidae) | Aphids, scales, thrips | Adults are pollinators; larvae are efficient pest controllers. |
| Praying Mantis (Mantodea) | Various insect pests | Generalist predator, consuming a wide variety of insects, including beneficials. |
| Soldier Beetle (Cantharidae) | Aphids, caterpillars, beetle larvae | Larvae and adults feed on a variety of pests; also pollinate plants. |
| Predatory Stink Bug | Caterpillars, beetles, aphids | Generalist predator that feeds on various pest insects. |
| Assassin Bug | Caterpillars, aphids, beetles | Effective against a variety of garden pests; care needed as they can bite humans. |
| Ground Beetle | Slugs, caterpillars, insect larvae | Nocturnal predators that are beneficial for controlling soil-dwelling pests. |
| Parasitic Wasp (Aphidius) | Aphids | Lay eggs inside aphids, eventually killing them and preventing further infestations. |
| Spider (Thomisidae) | Various insects | Ambush predators that do not spin webs; effective in controlling mites and other small insects. |
