Beneficial insects are a great asset to have in the garden, said Candice Miller University of Illinois Extension horticulturist.
“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. “Lady bird beetles for example, are a great beneficial insect to have in the garden because both the larvae and adults feed on soft-bodied pests like aphids, and are able to help control an infestation in the garden.
“There are also various parasitic wasps that lay their eggs inside pests like aphids or tomato hornworms. The larvae develop inside the pest, essentially killing it from the inside out.”
So 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 diverse selection of things to feed from, so start off by planting a diverse garden of fruits, vegetables, and flowers. Don’t simply plant the garden in rows. Instead try inter-planting 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, like Queen Anne’s lace, members of the brassica family, like broccoli, and herbs like dill, fennel, and coriander are all great plants with small flowers to put in the garden. Plants in the aster family like cosmos are great as well.
“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 desired 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 your garden pests are also going to kill your beneficial insects and may leave a residual that lasts the rest of the season.
“With just some simple planning early in the season of what to plant in the garden and some changes in practice, gardeners can take a step towards naturally controlling the pests in their gardens,” she said.