Metro-East Living

Can certain plants help keep bugs away? Experts weigh in.

Bugs' and bees' relationship to plants

If gardeners want bees and other pollinating insects, a variety of flowering plants that bloom throughout the year and a water supply are open invitations, says Jake Williams, associate professor at Southern Illinois University Edwardsville.
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If gardeners want bees and other pollinating insects, a variety of flowering plants that bloom throughout the year and a water supply are open invitations, says Jake Williams, associate professor at Southern Illinois University Edwardsville.

“There’s a spider!” says one of the four young sons of Jeff and Christi Pitts.

“Catch it!” another quickly responds to yet more excited chatter.

As the boys, ages 9, 7, 6 and 4, played outside and their 19-month-old sister dozed, Jeff gave a tour of their backyard garden, which is a lesson in both biological diversity and pest management.

“We do everything we can to not have mosquitoes,” Jeff said, which includes a goldfish pond that attracts insect-loving frogs. Goldfish love to eat mosquitoes, and frogs and toads eat insects as well. “We also have a bat house. It’s not inhabited yet, but we’re trying.”

Between the animals at their Fairview Heights home that feast on insects and careful planting management — he avoids bunching the same plants together to avoid attracting pests — there are few unwelcome bugs in the Pitts’ yard.

While some gardeners search for plants that repel pests — citronella, basil, lemongrass, catnip and parsley are all said to have properties that bugs dislike — some gardeners like Pitts and insect experts have other suggestions.

“We want our pretty flowers, but we don’t want the bugs that come with them,” says Sandy Richter, of Sandy’s Back Porch in Belleville. At the store, she sprays insecticide because “it’s a smorgasbord and people don’t want to buy plants with holes in them.” But at home, she “rarely” uses spray, making an exception for the occasional fungicide.

“I don’t think bugs are a big deal,” she said. “I think it’s all part of the natural ecosystem ... somebody eats somebody who eats somebody.”

We want our pretty flowers, but we don’t want the bugs that come with them.

Sandy Richter, of Sandy’s Back Porch in Belleville

The Pitts family keeps their animal areas clean and place similar plants apart, making it harder for a number of bugs to congregate in an area. Pitts researches plant varieties to get those naturally resistant to area insects. A lot of it is exercising what he calls “permaculture” principles, which he writes about on his blog, which can be found online at www.regenerativelandscaping.com/.

“We made the mistake of planting a Honeycrisp apple, which is the worst thing you can do” around here, he said, because the apple’s thin skin and high sugar content attracts bugs. They don’t have that issue with pear trees and haven’t yet with Fuji apples.

Most of what we think of as “bugs” aren’t even interested in bugging people, says Jake Williams, associate professor at Southern Illinois University Edwardsville.

“Most insects are herbivores,” he said. Which is rather lucky for us, given that there are some 200 million insects per person on the planet.

If it dares to suck my blood, it will lose its life.

Elizabeth Wahle, educator with the University of Illinois Extension Office

Williams studies the bug world, specifically researching how bugs use chemicals in hopes of finding ways to freeze human tissue for organ transplants.

Part of the biological research at SIUE is honeybees, which are not native to the United States but are integral to pollination. About a hundred thousand bees live in the colonies maintained at SIUE, and they all draw nectar for honey within a two-mile area, Williams said. Bees often swarm in spring, and Williams said those swarms won’t stick around more than a day or so.

“Swarms are relatively docile. Bees (get aggressive) to protect the home, and the swarm has no home to protect,” he said.

If gardeners want bees and other pollinating insects, a variety of flowering plants that bloom throughout the year and a water supply are open invitations, Williams said.

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Even the much-maligned mosquito world don’t all carry diseases. Of the 3,000-plus species of mosquito, “most” do not carry diseases. And only female mosquitoes even bite, the males feed off of plant nectar, Williams says. For one group, the 430 members of the genus anopheles, “10 percent can transmit things like malaria,” Williams said.

“I don’t worry about it when my kids get a mosquito bite,” he said, adding that if there were symptoms of illness he would take the child to a pediatrician.

Richter said Sandy’s Back Porch sells a lot of citronella and lemongrass to customers looking to combat mosquitoes, and she uses citronella in her own yard while dining outside.

“First you think, ‘oh, there’s not much to it,’ but we’ve sold it over and over again. If it didn’t work then people wouldn’t be buying it,” she said.

Williams is hesitant to recommend plants to repel insects.

“There’s not much of a huge effect. Plants produce chemicals to keep themselves from being eaten, but it doesn’t extend” to the people around the plant, he said.

He thinks the popularity of the citronella plant is a “placebo” effect. Besides, the citronella candle? That scent is made from lemongrass, he said.

“Now if you were to grind up that plant and apply it to your skin... but you could be putting on very little or way too much” of the chemical that repels insects.

“People say ‘Well it’s all natural.’ Snake venom is all natural,” he said. “I use DEET, the only thing commercially available. You know what you’re putting on, and has a consistent ... effect on mosquitoes.”

The upside to all those flying and crawling critters in the yard is what comes after them, says Elizabeth Wahle, an educator at the University of Illinois Extension Office in Collinsville, talking about the food web that includes songbirds.

“It becomes kind of exciting when you seen an assassin beetle grabbing hold of a Japanese beetle and taking care of it naturally,” she said.

Wasps and dragonflies are also predatory bugs.

“I’m thinking, as someone concerned about the environment, there are a lot of bats and birds that rely on (bugs) for food. I don’t want to discount diseases (such as zika) but they are an integral part of the food web.”

Part of the food web or not, Wahle draws the line firmly at her own skin.

“If it dares to suck my blood, it will lose its life,” she said.

Don’t want bugs?

Don’t have flowers. Bees and insects are attracted by the plant, many of which emit chemicals to invite the bugs to pollinate.

Don’t have water. Mosquitoes breed in water; but so do dragonflies, which are predators to other insects. Even the very young dragonfly still in water will open it’s jaws wide to chomp on other bugs, says Jake Williams, associate professor at Southern Illinois University Edwardsville.

Do have weed barrier fabric. Ground-dwelling insects can’t burrow through the fabric. That includes ground-dwelling bees, and wasps that are predatory to other insects.

Do have grass. Lawn grass kept short “is like concrete” to an insect, Williams said, offering little to insects.

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