The Homeowners Column

The Homeowners Column

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Bee friendly to beneficial insects in the garden

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Sandra Mason
State Master Gardener Coordinator
slmason@illinois.edu

The good, the bad and the bugly. Despite common horror show depictions not all bugs are bad. Outside of horror flicks the likelihood of a bug crawling into your ear and sucking out your brains is pretty remote. To some the only good bug is a dead bug. However, a tiny percent of insects are actually pests to people and plants. We take for granted the many services insects provide. Some insects are directly beneficial by pollinating the food that makes our lives worth living. Other beneficial insects include predators or parasites of other insects that harm us or our plants. Even insects have enemies.

Insect predators and parasites (more correctly termed parasitoids since they kill their host) are the unsung and often misidentified heroes of the garden world. Predator insects include hover fly larvae, ladybeetles, lace wing larvae, robber flies, and even the tiny pirate bugs. These are the lions of the insect world as they "stalk" unsuspecting aphids and caterpillars. Hover fly (sweat bee) adults are very common in summer. Despite their bad ass black and yellow coloration, they are flies and cannot sting.

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Parasitic insects such as parasitic wasps are extremely important beneficial insects for controlling our plant pests. They are often very specific to certain pests. For example, the infamous tobacco or tomato hornworms can quickly defoliate a tomato plant. Sometimes you may see a hornworm with what looks like rice attached to the caterpillar. These are the cocoons of a tiny braconid wasp. The adult wasp lays her egg inside a young caterpillar. As the caterpillar grows so do the baby wasp larvae as they happily munch away on the inside of the caterpillar, leaving the important parts for dessert. In true horror film fashion eventually the wasp larvae bust through the caterpillar skin and weave silken cocoons on the outside of the caterpillar. Soon the adult parasitic wasps emerge from the cocoons to find another victim. Be sure to leave these cocoon covered caterpillars on your tomatoes so the wasps can continue their life cycle. Parasitized hornworms eat about one fifth of the tomato leaves compared to the voracious appetites of non-parasitized caterpillars.

The good news is we can help the beneficial good guys in our gardens in much the same way we help pollinators.

First learn how to recognize common beneficial insects. A great reference is the laminated card set "The Good Guys! Natural Enemies of Pests" available through UI Pubs Plus 800-345-6087 https://pubsplus.illinois.edu/

Minimize or eliminate insecticide applications. Many insecticides can kill beneficial as well as pest insects. Always read and follow label directions.

If insecticides are chosen as a control method, use selective insecticides. Selective insecticides are toxic to specific pests and will not directly harm beneficial insects. The microbial insecticide Btk sold as Dipel and Caterpillar Attack are only toxic to caterpillars feeding on the sprayed plants. Insecticidal soaps can also be effective on pest insects without harming beneficials.

Build it and they will come. Include a diversity of plants in the landscape with something blooming throughout the season. Include annual and perennial flowers, native grasses, ground covers, shrubs and trees.

Plant a variety of flowers with various flower shapes and sizes and include lots of native plants. Exotic plants will provide nectar and pollen; however, native plants will attract more beneficials. Many beneficials feed on pollen and nectar or use flowers to supplement their food supply if they run low on pests.

Plants in the carrot family and mustard family are especially attractive to small parasitic wasps. Small flowered plants include: candytuft; golden alexander; New Jersey tea; sweet alyssum; dill; coriander (cilantro) and white lace flower. Other popular plants for beneficials and pollinators include: asters; beebalm; columbine; white wild indigo; blanket flower; coneflower; coreopsis; cosmos; tansy; yarrow; goldenrod; mints; penstemon; sedums and sunflowers.

Be friendly with beneficials in your garden.

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