Sally Scalera

Brevard County Horticulture Extension Agent
3695 Lake Drive -- Cocoa FL 32926 -- 321-633-1702

Beneficial insects

July 16, 2005

I would be willing to bet that everyone would love to have a little free pest control in their yard. An easy way to achieve this would be to grow the plants that attract beneficial insects. Beneficial insects can be divided into two groups. Predatory insects that eat the harmful bugs and parasitic insects that lay their eggs in or on the bad bugs. When the eggs hatch, the larvae eat up the bad bug! Generally, it is the larval stages that eat the most pests.

Many people buy beneficial insects and release them in their yard. An easier and more inexpensive way to achieve the same result is to create habitats throughout your landscape that support the beneficial insects all year long. The main way to create a habitat for beneficial insects is to plant flowers that will provide food in the form of pollen and nectar for the adults. Tiny flowers, like those found on herbs, provide the best pollen and nectar for beneficial insects. Because many of the beneficial insects are small, tiny flowers are easiest for them to feed from.

Here is a list of some of the herbs that have flowers that are known to attract beneficial insects: Dill (Anethum graveolens) annual; Cilantro/Coriander (Coriandrum sativum) annual; Queen Ann’s lace (Daucus carota var. carota) annual; Basil (Ocimum basilicum) annual; Alyssum (Lobularia maritime) winter annual; Fennel (Foeniculum vulgare) perennial; Yarrow (Achillea millefolium) perennial; Garlic chives (Allium tuberosum), Anise hyssop (Agastache foeniculum) annual; Lovage (Levisticum officinale) perennial; Angelica (Angelica archangelica) biennial; Parsley (Petroselinum crispum) biennial; Tansy (Tanacetum vulgare) biennial; Cosmos (Cosmos bipinnatus) annual; Mints (Mentha spp.) perennial.

There are a number of different ways that you can use these flowers, such as plant them in rows among your vegetables, create wide borders around the outside of your vegetable garden or shrubs, or place “island” plantings in the middle of a vegetable garden or landscape. Some vegetable plants, when allowed to flower, will also attract beneficials. These include broccoli, lettuce, other greens, bok choy and corn. If you like to grow broccoli, you may want to let the side shoots grow and flower after harvesting the main head.

Another good source of food for beneficial insects are cover crops (which are legume or grain crops that are planted between rotations of garden crops to improve the soil and prevent erosion) and living mulches (the same plants but, used as a ground cover under trees and shrubs to suppress weeds and shade the soil.) Some examples are crimson clover, hairy vetch and white Dutch clover. White Dutch clover can even be mowed regularly to keep it blooming throughout the year.

In addition to all of these plants, there is also a flowering landscape plant that can be added to the landscape to attract beneficial insects. Dr. Russ Mizelle, an entomologist with the University of Florida, feels that crape myrtles (Lagerstromia indica) are probably the most important woody landscape plant in the southeastern United States for augmenting and sustaining may beneficial insects. There is an aphid which only attacks crape myrtles, so you don’t have to worry about them spreading to any other plants.

Approximately 13 predatory beneficial insects are attracted to the crape myrtle to feed on the aphids. The crape myrtle provides food for the beneficials during the times when your other plants are pest free. (As a matter of fact, ladybugs and green lacewings cannot lay eggs unless there is sooty mold present!) When other pests show up in other parts of your landscape, the predators will be nearby and ready to attack.

If you do “garden” for beneficial insects, try not to use harsh pesticides that not only kill the harmful pests but also the beneficials. Ultra-fine horticultural oil or insecticidal soap works well for controlling the piercing-sucking insects such as aphids, whitefly, scale and mealybugs. The oils and soaps don’t leave harmful residues that kill beneficials even after they have dried. Just one note of caution, make sure that any plant being sprayed with soap or oil has been watered thoroughly.