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Good Bugs, Bad Bugs

By Tom Brinda and Lynn Kirk, Lewis Ginter Botanical Garden

It’s inevitable. Plant a vegetable garden and insects will come. So how should environmentally conscious gardeners respond? They should begin by increasing their knowledge and understanding of insects, suggested entomologist Dr. Karen Kester, a Virginia Commonwealth University associate professor of biology.

“Just because a bug is on your plant doesn’t mean it’s eating your plant,” Kester said. “Learn to identify insects because there are good bugs and then there are bad bugs.”

“Good bugs” are those that benefit the garden by aiding the pollination process, such as bees and butterflies. Other insects considered beneficial are natural predators - those that reduce populations of unwanted insects by eating sometimes hundreds of adult pests or their larvae every day. For example, lady beetles, lacewings, hoverflies and predatory bugs and wasps should be welcomed in the garden because they are natural predators of unwanted insects, such as aphids, mites and caterpillars that can reduce harvests and even ruin entire crops.

“As a society, we tend not to like bugs,” Dr. Kester said. “But don’t just kill them—learn about them. Insects and plants are all wonderfully interconnected and understanding what insects are doing in your garden increases your tolerance and appreciation for them.” To help gardeners with insect identification, Kester recommends two websites with color photos: www.whatsthatbug.com and www.bugguide.net.

Other eco-options for insect control

If unwanted insects are identified and their numbers are unacceptable, gardeners should still resist the urge to apply harsh pesticides. Chemicals in broad-spectrum insecticides can be non-discriminate, sometimes killing not only the targeted pest insects but also the beneficial ones. Research demonstrates that over-application of pesticides over time also adversely affects the environmental balance of insects and soil organisms and can result in pesticide resistance. 

Instead of strong chemicals, organic gardeners often recommend insecticidal soaps and oils that can be highly effective and environmentally sound. As with chemical pesticides, best results are based on the type of plant and insect, as well as application at the proper time in the insect’s life cycle.

Another way to reduce the number of “bad” bugs is to grow mixed plantings and flowering plants around the garden border. These borders provide nectar for honey bees and other native bees. Also, they double as a food source and shelter for parasitic wasps, encouraging them to take up residence, multiply and naturally assist in reducing the number of unwanted insects. Companion plantings of buckwheat near vegetable gardens are especially appreciated by tiny parasitic wasps. Other plants, such as marigolds, produce natural chemicals that kill nematodes that can infest roots of tomato plants. 

Dr. Kester further recommends that “gardeners should consider which plants are ‘right’ for their locality and growing zone. Whenever possible, select hardy plants that are most resistant to insects and disease.”

For additional information on eco-friendly insect control, contact your extension agent or visit the library at Lewis Ginter Botanical Garden.