When planning your garden this spring, consider growing some plants that will help attract natural enemies of insect pests, said University of Illinois Extension educator Ken Johnson.
“Attracting natural enemies to your garden can help reduce the amount of pest problems you encounter,” Johnson said. “Natural enemies will attack pest insects such as aphids, whiteflies, scale, mealybugs, thrips and small caterpillars.”
There are two ways insects act as natural enemies. “People are most familiar with predators such as lady beetles,” Johnson said. “Predators will consume many insects over their lifetime. In addition to lady beetles, insects like minute pirate bugs, lacewing larvae, and hoover fly (syrphid) larvae act as predators.
The other type of natural enemies is parasitoids. Johnson explained that parasitoids will lay eggs on, in, or near their insect host. Once the eggs hatch, they will enter the insect and consume it, eventually killing it. Insects that act as parasitoids are primarily tiny wasps and flies.”
“In addition to prey, many natural enemies need sources of pollen and nectar,” he added. “These sources are especially important for parasitoids, as well as the adult stages of insects with predaceous larvae. By planting plants that are attractive to these natural enemies, you can help encourage them to stick around.”
Flowers that are good for attracting natural enemies are usually small, relatively open plants such as those in the carrot (Umbelliferae) and aster (Compositae) families. Plants in the carrot family tend to have flower heads that are white or yellow with large flat heads that provide good landing places for insects. “There are a number of herbs in this family such as dill, cilantro, fennel, and caraway that can be used,” Johnson said. “Avoid using Queen Anne’s Lace because it can become rather weedy. Many of these plants can rapidly spread if they are allowed to go to seed so it is a good idea to remove the seed heads before this happens”
Plants in the aster family have flower heads that are made up of many small flowers. Many commonly grown flowers such as coneflower, sunflower, cosmos blanketflower, yarrow, and coreopsis are in this family and will help keep natural enemies around.
“Just like in pollinator gardens, you want to plant clumps of plants that bloom at different times,” Johnson explained. “This will provide natural enemies with sources of pollen and nectar throughout the growing season.”
Other natural enemies such as praying mantises, wasps, ground beetles, and larger parasitic wasps are more mobile so their presence is less dependent on flowering plants. However, many will also use nectar and pollen as food sources.
It is also important to avoid spraying pesticides on your plants. “After all, that’s what you are attracting the natural enemies for,” Johnson said. “It will take some time for natural enemies to find your pest populations so you may need to be patient and be willing to accept some damage to your plants. If you feel pesticides must be used, contact your local U of I Extension office for pesticides that are safer to use around natural enemies.
“With a little help from your natural enemies can help keep your pest problems under control,” he added.