Attract Beneficial Insects to Your Garden

Helen Brandt is a plant propagator for Wintergarden Nursery in Bellingham. Contact her at helenbrandt@comcast.net.

There are a variety of beneficial insects that parasitize or predate (eat) pests that harm your plants. Beneficial insects include assassin bugs, ladybug beetles, pirate bugs, parasitic wasps, hoverflies, syrphid and tachinid flies, lacewings and ground beetles.

You can attract these helpers to your garden by growing flowers that provide pollen, nectar and shelter for them. In order to provide food through the season, try to choose plants that bloom at different times. Choose flowers that have a single circle of petals, rather than fancy layered, multi-petal varieties. Beneficial insects often are tiny and need the pollen or nectar to be near the surface of the flower. Flat or disk shapes are useful.

Plant your insectary flowers in large clumps, rather than scattering them here and there or lining them up in a row. Avoid using insecticides because they will kill the beneficial insects you want to work for you.

If your vegetables begin to flower (bolt) in the hot weather, let them do it! They will attract small insects that like their simple, open flowers. Let collards over-winter and flower in their second year; you will attract myriads of beneficial insects.

Researchers have discovered some amazing things about plant/insect relationships. In one study, they found that when a caterpillar begins eating the leaf of a plant, the mechanical damage and a chemical in its saliva alert the plant of the harm. The plant then begins producing a volatile chemical that wafts into the air.

Beneficial parasitoid insects in the area begin to notice the smell and follow its intensity until they find the plant under attack. They then parasitize the feeding caterpillar, ultimately killing it.

Researchers also discovered that when high nitrogen fertilizer is used with a crop such as cotton, the plant does not release enough of the volatile chemical. Beneficial insects are less likely to locate it and the cotton plant is less able to protect itself from attack.

Encourage beneficial insects to do their bug-fighting work for you. Enjoy the flowers and save money on pesticides.