By Ken Johnson
Not all of the insects you see in your garden are pests. There are a wide variety of beneficial insects that you can find in your garden. These insects can be broken up into 2 different groups: generalists and specialists. Generalists such as lady beetles, praying mantids, assassin bugs, lace wings and hover flies will consume a wide variety of garden pests. In some cases, like with lady beetles and praying mantids, both the larvae and the adults will consume insects. In other cases, like with lace wings and hover flies, only the larvae will consume insects. Specialist insects like parasitoid wasps will only attack one type of insect, or in some cases, one species. The adult wasps will look for the eggs or larvae of their target. Once they have found them, they will lay their egg on the insect or inside of it, depending on the wasp. Once the wasp egg hatches it will start to develop inside of the insect and eat it, eventually killing the insect.
To keep these beneficial insects around your garden, there are several things you can do: Reduce the amount or eliminate the use of insecticides you are using. Most insecticides will kill beneficial insects as well as pests.
If you are going to use insecticides, use a selective pesticide. These pesticides are toxic to specific insects and won’t directly harm beneficial insects. For example, Bacillus thuringiensis (Bt), sold as Dipel Bt and Caterpillar Attack, is only toxic to caterpillars. When using pesticides make sure to read and follow all label directions.
Provide flowers for the beneficial insects to feed on. Many of the beneficial insects will feed on nectar and pollen, this is especially important if the adults aren’t predators. Plants in the carrot and mustard families are very attractive to beneficial insects. Plants with small flowers such as sweet alyssum, dill, fennel, garlic chives, coriander and Queen Anne’s lace are good choices. Other common garden plants like blanket flower, coneflower, cosmos and sunflowers will be visited by beneficial insects too.