Attracting Beneficial Insects

Unless you regularly use broad-spectrum insecticides, they are already more active in your garden than you realize.

Some Common Beneficial Insects

• Lady beetles and praying mantises are the ones we typically recognize.
• Parasitic wasps, some of which are smaller than the period at the end of this sentence. Still, others are parasitic flies that resemble houseflies. You may have even swatted a few of them, thinking they were nuisance pests.
• Ground beetles look fierce and may be mistaken for bad guys, but they are important predators of many pests, including gypsy moth larvae and many soil-dwelling insects.
• Adult flower flies may be mistaken for yellow jackets, but they do not sting; their larvae are voracious aphid predators.

Many species of beneficial insects are available commercially and are becoming increasingly popular to help control pests in greenhouses. The U.S. Department of Agriculture, in conjunction with agricultural research stations, has introduced predators and parasites of foreign pests that were accidentally introduced into this country. These include:

• tachinid flies that are parasites of spongy moth larvae (formerly gypsy moth larvae)
• twice-stabbed lady beetles that are predators of scale insects
• Vedalia beetles that are predators of cottony cushion scale on citrus

While buying and releasing beneficials can help control large populations of insect pests, a better approach in the home garden is to attract and encourage existing populations of beneficials. The most important thing you can do to protect and encourage beneficial insects in your garden and landscape is to choose insecticides carefully. Many beneficials are more sensitive to insecticides than the pests you are trying to control. While it is true that beneficials can reduce your pesticide use, realistically, you will still have to use pesticides to deal with serious pest outbreaks from time to time. The key is to choose products that have little or no residual activity. While the beneficials present when you spray will be killed, new ones coming into your garden will not be affected.

These insecticides include:

• insecticidal soap
• horticultural oil
• botanical insecticides such as neem, pyrethrins, rotenone, and sabadilla.
  The botanicals do have brief periods of residual activity, but they are much shorter than most synthetic insecticides. Most break down rapidly when exposed to the sun.

Having as much diversity as possible in your plantings is also important. A mix of trees and shrubs, turfgrass (yes, low-maintenance turf is an important habitat for some beneficials!), and annual and perennial flowers is best. Permanent plantings such as trees, shrubs, and turf provide a place for beneficial insects to overwinter. The adults of many beneficials feed primarily on pollen and nectar, so it is important to have something in bloom from early spring until late fall.

Some of the Best Flower Families for Attracting Beneficials

• Carrot Family (Apiaceae)

  plants in the carrot family are especially attractive to small parasitic wasps and flies. Interplant them in your vegetable garden and flower beds. Plants in this family include caraway (Carum carvi); coriander/cilantro (Coriandrum sativum); dill (Anethum graveolens); fennel (Foeniculum vulgare); Bishop's flower (Ammi majus); Queen Anne's Lace (Daucus carota); and toothpick ammi (Ammi visnaga).

• Aster Family (Asteraceae)

  attractive to larger predators such as lady beetles and soldier beetles. Incorporate into the vegetable garden and flower beds. Plants in this family include blanketflower (Gaillardia spp.); coneflower (Echinacea spp.); coreopsis (Coreopsis spp.); cosmos (Cosmos spp.); golden marguerite (Anthemis tinctoria); goldenrod (Solidago spp.); signet marigold (Tagetes tenuifolia); sunflower (Helianthus spp.); tansy (Tanacetum vulgare); and yarrow (Achillea spp.).

• Legumes (Fabaceae)

  generally grown as cover crops and attractive to many beneficials. Plants in this family include alfalfa (Medicago sativa); fava bean (Vicia fava); hairy vetch (Vicia villosa); and sweet clover (Melilotus spp.).

• Mustard Family (Brassicaceae)

  attractive to beneficials that are parasites and predators of the insect pests of the mustard family (broccoli, Brussels sprouts, cabbage, cauliflower, kohlrabi, mustard greens). Be sure to plant these away from the garden rather than in the garden since these plants attract pests as well as beneficials. Some are common weeds, such as yellow rocket and wild mustard. Plants in this family include basket-of-gold alyssum (Aurinia saxatilis); mustards (Brassica spp.); sweet alyssum (Lobularia maritima); yellow rocket (Barbarea vulgaris); and wild mustard (Brassica kaber).

• Verbena Family (Verbenaceae)

  attractive to a variety of beneficial insects. Many plants in this family are favorite garden flowers. They include lantana (Lantana camera); Buenos Aires verbena (Verbena bonariensis); hybrid verbena (Verbena x hybrida); and lilac vervain (Verbena rigida).

Beneficial insects also need a source of water. Shallow containers such as ceramic pot saucers with pebbles for the beneficials to rest on are best.