Garden helpers: Grow plants that attract beneficial insects

07/03/2014 2:55 PM

07/05/2014 7:47 PM

Summer is here, but it is still early enough to build a good defense against nasty plant-munching insects in the garden.

Gardeners nationwide spend more than $4 billion a year ridding the environment of pesky insects, which swoop in with big appetites to devour our hard work and spoil our backyard oases. Gardeners spray pesticides, and the insects decline slightly, only to return the next year with more ferocity and bigger appetites.

This cycle creates a system in which pests grow more tolerant of our chemicals than their parents’ generation. So we keep inventing stronger sprays and spray more of them.

To solve this problem, gardeners are growing flowers and plants that attract beneficial insects. Naturally occurring, and often free, beneficial insects are predators to our worst landscape insect foes, and most are pollinators for our favorite flowers, fruits and vegetables.

Ami Zumalt of Odessa, a certified organic farmer and owner of Red Ridge Farms, has a special relationship with beneficial insects. “They are the good guys — my primary line of defense,” she says. “They devour the bad bugs that eat my plants. Beneficial insects pollinate flowers, so I have increased crop production.”

Implementing a plan to attract beneficial insects is easy. Any space, whether it’s a large suburban yard or a window box outside an apartment, can take part in this eco-friendly practice.

Remember the lesson that Dorothy learned in “The Wizard of Oz”? That what she was searching for was there the whole time? The same goes for Kansas City, which is chock-full of beneficial insects. There are more than 1 million species of insects in the world, and only less than 1 percent are considered harmful, Zumalt says. If you plant the right plants, beneficial insects, such as ladybugs, will stay and colonize around your home.

Aphids are a pest to many plants in a typical American garden, such as roses, crape myrtles and most summer vegetables. When they pierce into the soft plant tissues, they have the ability to spread diseases from plant to plant.

Ladybugs are an icon to gardeners who loathe aphids. Gardening T-shirts, gloves and boots are adorned with their images — polka dots are always “in” in the garden. These garden superheroes are treated with admiration because of their amazing appetite for aphids.

“When aphids were causing the new growth on my honeysuckle to curl, I just waited for the ladybugs to find them and take care of the problem,” says Jackie Goetz, Johnson County K-State Research and Extension master gardener.

In her garden, Goetz specifically grows pollen- and nectar-rich flowers that ladybugs are strongly attracted to. She knows that when a problem arises, these small red beetles with their signature spots will swoop in and eat the aphids.

Another well-known beneficial insect is the praying mantis. They often steal the spotlight because of their easily recognizable mandibles and spiky forelegs.

Immature mantises eat smaller insects, but they graduate to larger prey as adults, when they are 5 to 6 inches long. Some large mantises have been known to eat snakes and rodents later in the summer.

Experienced gardeners know the worth of ladybugs and praying mantises, but what about other, lesser-known beneficial insects? Underdogs such as green lacewings, hoverflies and parasitic wasps are constantly working to keep the pests down in your garden.

“The workhorse in my garden is the green lacewing. The adult form is beautiful with its clear green membranous wings,” says Chris Veach, emeritus Missouri master gardener.

Green lacewings lay their minute eggs near colonies of destructive aphids. When the larvae hatch, they are sometimes called “aphid lions” because of their voracious appetites. Ferny-leaved herbs, such as coriander and dill, are great for attracting the green lacewing.

Another lesser-known beneficial insect Veach appreciates is the hoverfly. During her lectures for the Master Gardeners Speakers Bureau, Veach lists the hoverfly as one of the top 10 best beneficial insects in the garden.

Hoverflies have clear wings like the green lacewing, but to protect themselves from birds, their bodies and coloration resemble a yellow jacket. Many hoverflies have been mistakenly killed because of this resemblance.

When hoverflies aren’t retreating from cans of Raid, they can be found devouring soft-bodied nuisances such as aphids and thrips. Plant classic garden beauties like cosmos and zinnia, and hoverflies will be buzzing by your garden all summer long.

Another garden helper is the parasitic wasp. They are some of the smallest insects — they range in size from 1 millimeter to 1 inch long and have tiny, inconspicuous bodies.

Horticulturist Matt Bunch of the Kansas City Community Gardens’ Giving Grove program lists parasitic wasps as one of his favorite beneficial insects.

“Many of these species of wasps lay eggs within a host, like the fruit moth caterpillar. Then the young eat the host, spin a cocoon and emerge as adults,” Bunch says.

“If you are planning on fruit trees, sunflowers can be a useful tool in your pest management toolbox.”

The adult parasitic wasps flying about will be attracted to the nectar in the flowers, and if they see the opportunity to lay their eggs in a nearby pest, they will take it. Even if you don’t have any problems with your apple trees, a few extra sunflowers in the yard are always a welcome sight.

Jan Curry of Overland Park, a Johnson County K-State Extension master gardener, suggests cultivating a diverse and season-long habitat. She often refers to lists published by the K-State Extension office and the Kansas Native Plant Society when she needs ideas for new plants to attract beneficial insects.

She also adds, “One of the biggest side benefits I have seen is the increase in the number of birds that come to my garden.”

That’s another lesson that gardeners have learned from the decades of dependency on harmful chemicals in the garden: Birds, bees and butterflies also benefit from the ecosystem that protects beneficial insects.

“I can’t think of a better way to start my day than watching a butterfly and listening to a bird sing,” Curry says. “Unless it is seeing the joy on my grandchildren’s faces as they look at a monarch caterpillar.”

Luring beneficial insects

There are hundreds of striking blooms to choose from that will attract beneficial insects to your yard.

Cosmos, marigolds and bachelor’s buttons are among the best money-saving choices. Although they live for only one season, these nectar-rich blooms will re-seed in the garden year after year.

“Some of the best plants are the ones that have a long flowering time, large blossoms and a heavy supply of pollen and nectar,” says Matt Bunch of the Giving Grove program at Kansas City Community Gardens.

Herbs such as anise hyssop, fennel, dill, parsley and cilantro have flowers that contain the sugars adult insects need for energy to hunt and lay eggs in your garden. They’re also great for pollinating insects such as bees and butterflies.

Garden perennials also play a role in attracting beneficial insects. The succession of blooms that open with each season keep the insects happy the whole growing season long. And if you plant them once, they will come back every year to help you keep a healthy garden. Aster, catmint and coreopsis are easy to grow in Kansas City, and they are attractive to these helpful insects.

Native plants, such as serviceberry and ninebark, supply early-season nectar and pollen, whereas beautiful flowers such as goldenrod and echinacea put on a show later in the season.

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