URBANA -- Beneficial insects are an asset to the garden, said a University of Illinois horticulture educator.
“Beneficial insects are naturally occurring insects that help control garden pests, whether by eating the pest, eating the pest’s eggs, or parasitizing the pest,” said Candice Miller. “Ladybird beetles, for example, are a great beneficial insect to have in the garden because both the larvae and adults feed on soft-bodied pests such as aphids and are able to help control a garden infestation.”
There are also various parasitic wasps that lay their eggs inside pests such as aphids or tomato hornworms. The larvae develop inside the pest, killing it from the inside out.
How can you attract these naturally occurring beneficials to your garden?
“Start planning now what you’ll plant in the garden,” said Miller. “Beneficial insects like to have a selection of things to feed from, so start off by planting a garden of diverse fruits, vegetables, and flowers. Don’t simply plant the garden in rows. Instead, try interplanting your fruits and vegetables with flowers throughout the garden.”
Parasitoids need to feed on nectar, honeydew, and pollen in particular, and they prefer to feed from plants with small flowers. Sweet alyssum, members of the carrot family such as Queen Anne’s lace, members of the brassica family such as broccoli, and herbs such as dill, fennel, and coriander are all plants with small flowers. Plants in the aster family such as cosmos are also suitable.
“One may also consider planting marigolds or pepper plants around the garden to serve as trap crops,” said Miller. “These plants are there to attract the garden pests away from your other garden plants. The marigolds and pepper plants can then be removed, treated with pesticides, or kept in the garden to maintain pest populations for beneficial insects to feed from.”
Reducing the use of chemical pesticides in the garden is also essential. Most pesticides that kill garden pests are also going to kill beneficial insects and may leave a residue that lasts the rest of the season.
“With just some simple planning early in the season of what to plant and some changes in practice, gardeners can take a step toward naturally controlling the pests in their gardens,” she said.
For more information regarding beneficial insects, visit the U of I Extension website at http://web.extension.illinois.edu/state/index.html.