Beneficial insects: How to attract good bugs to your garden
Suggestions include choosing a diverse variety of plants and letting some vegetables go to seed.
Fri, Mar 23 2012 at 11:11 AM
Small yarrow flowers can attract tiny parasitoid wasps, which feed on harmful aphids, caterpillars and beetle larvae. (Photo: nayukim/Flickr)
Not all bugs are bad, and knowing which is friend and which is foe may be more important than ever to gardeners this year.
That’s because entomologists are anticipating an increased number of insects this spring and summer due to what the National Weather Service says is the fourth mildest winter on record.
“A proportion of overwintering larvae, pupae, eggs, etc., get knocked back in winter, and the more severe the winter the greater the proportion that does not make it through,” said Jim Costa, director of the Highlands (North Carolina) Biological Station and professor of biology at Western Carolina University in Cullowhee. “I figure that we'll have a good spring emergence of insects as a result — the good, the bad, and the ugly.”
Which are good, which are bad?
While all insects might be ugly to many homeowners, knowing which are good and which are bad and attracting the good guys to eat the bad guys can be critical first steps to gardeners trying to grow that prize-winning rose or unblemished tomato.
Allison Mia Starcher, a garden illustrator and author, taught herself the difference when she was drawing illustrations of beneficial insects for the Southern California Gardener newsletter. She shared what she learned in an easy-to-understand book she wrote and illustrated, “Good Bugs for Your Garden” (Algonquin Books of Chapel Hill, 1995).
Speaking recently during a drizzling rain in the garden at the Santa Monica, Calif., house that used to belong to her maternal grandparents and where she now lives, Starcher said there are two ways for backyard gardeners to tell good bugs from bad ones: observation and Internet searches.
Pausing for a moment to marvel at parasitic wasps drawn to the pollen on flowers of mustard greens, Starcher said gardeners should “watch the bugs on their plants and see what they are doing.” This is a process she calls micro-level gardening and one from which she says she gets a satisfaction that cannot be overstated.
Eating or defending
To help distinguish between harmful and beneficial insects, Starcher said, gardeners should ask themselves which bugs are eating their garden and which ones are defending it.” Think, too, she urged, about what kind of damage is being done. Are holes being chewed in leaves? And when is the damage happening – for example, are the insects active at night?
If you see the bug, Starcher says to take a photo of it and write a short description. As an example, she suggested something as simple as “shield-shaped with red markings.
Armed with a photo, a description of the bug and its activity, Starcher said Web searches will often lead to bug ID sites. “I’m a real believer in asking questions and doing an Internet search,” she added.
“You can even do this on Facebook,” she pointed out. Perhaps your gardening friends can ID a bug or forward the information to someone who can.
More ways to ID
Other ways to ID bugs are to email a photo and description of characteristics to your local cooperative extension service. Better yet, Starcher advises, capture the critter and take it in a sealed baggie to a garden center. Once there, ask the staff for help in determining whether it’s beneficial or harmful.
The goal, she said, is to figure out which ones are the good ones … and don’t kill them.
To attract good bugs to the garden, Starcher and Costa offered several suggestions:
Make your garden as diverse as possible. The different nectars and pollen will attract a variety of insects. A byproduct of a richness of diverse plants and insects is that they in turn will create a healthy backyard ecosystem that will benefit birds, small mammals, reptiles and amphibians.
Use specific plants to attract specific insects. To attract zebra swallowtail butterflies, for example, plant paw paw trees, the only host plant for this species of butterfly.
Leave an occasional, dreaded weed undisturbed. Weeds add to the diversity of plants and thus increase the variety of insects in the garden.
Let vegetables, greens and herbs go to seed when possible. This is easy to do by peeling leaves from stems of plants such as arugula, basil and chard and leaving the stem to continue to grow and flower, attracting insects when it does.
Include plants whose flowers have an umbrella shape. Umbrella-shaped flowers have clusters of very small flowers and are accessible to tiny parasitoid wasps, which feed on harmful aphids, caterpillars and beetle larvae. The yarrow flower is an example.
Go native in the ornamental garden. Native plants are especially proficient at attracting pollinators and blooming when the pollinators are active.
Plant in vertical layers. Place plants such as alyssum and catmint under roses to attract beneficial insects such as ladybugs and lacewings. These beneficial insects consume pollen in their adult incarnations while their larvae eat pest insects. They are also efficient pollinators.
Don’t fret about ants (except fire ants). They add to the mutualism of ecosystems, harvesting and dispersing seed and extending the life of plant populations.
Rejoice in earthworms. While not an insect, they aerate and enhance soil.
If you can’t put enough good guys into your garden to combat the bad guys, there are organic pesticides as well as a variety of insecticidal soaps on the market that are safe for people and pets.
You can also engage in what Starcher calls hand-to-hand combat, squishing bugs with your fingers. “While we were talking,” she said during our call, “I squished a caterpillar Beet Armyworm” on a beet seedling.
Of course, there’s also an ecological advantage to leaving caterpillars and other “bad bugs” that chew on plants to meet another fate. “Basically, from a migratory bird point of view, the spring emergence of caterpillars and sawflies alone is like manna from heaven – nestling birds desperately need all those caterpillars to feed their hungry young,” Costa pointed out.
Whether through careful attention to creating a micro-garden haven for beneficial insects or through the Darwinian approach of natural selection, gardeners can rest easy knowing there’s a way to help the good bugs win and send the bad ones packing.
What attracts good bugs
Starcher, the author of “Good Bugs for Your Garden” prefers to use flowering herbs and wildflowers to attract insects to gardens because she believes that hybrid bedding plants have lost some of the characteristics that attract bugs. Those characteristics are nectar and pollen. Here are some of the herbs, vegetables and flowers she suggests will attract a wide variety of insects:
- Baby’s breath
- Lemon balm
- Queen Anne’s lace
- Rose-scented geraniums
- Sweet alyssum
Got other tips for attracting beneficial insects to the garden? Leave us a note in the comments below.
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