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Organic pest control: 5 safe ways to keep bugs out of your garden

Marigolds by tomatoes. Garlic next to roses. Sage nestled near your taters.

While the concept of companion planting has been touted by some as an organic approach for repelling pests from gardens, research doesn’t support the hype, according to experts in gardening and entomology at The Ohio State University.

“It’s really hard to say that (companion planting) does work,” says Celeste Welty, who researches pest control in Ohio State’s College of Food, Agricultural and Environmental Sciences. “If anything, (pests) love garlic; they eat more.”

But don’t despair: Welty and master gardeners offer these other steps you can take to get rid of pests without chemicals — while embracing and maintaining a healthy ecosystem in your garden.  

  1. Take matters into your own hands.
    Hand holding bug, The Ohio State University

    Spare the spray. Remove the pests yourself.

    For some pests, such as the potato beetle, Welty suggests walking down the row and shaking plants or tapping them with a small broom. When the beetles fall off, catch them in a bucket. 

    You can also buy a small aspirator. It allows you to suck up insects through a tube, but a screen keeps you from inhaling them. “I’ve had extremely good luck using this with eggplant flea beetles,” Welty said, adding that it can take just a few minutes a day.

    For squash bugs, place a piece of wood or a shingle at the base of the plant. Welty said the bugs like to take cover under it at night. In the early morning, pick up the board and end their squash-eating careers.  

    It’s important to catch pests early before they get out of hand, so inspection is key, said Pam Bennett, an OSU Extension educator and associate professor at Ohio State.

    “Many times people wait until they actually see damage on the plant or it’s too late,” Bennett said, “and then you end up maybe resorting to pesticide because you haven’t been paying attention.”

  1. Change your perspective.
    Friendly bug, Spider in web around Pepper plant, The Ohio State University

    Some insects are unwanted guests, but not all of them have to be.

    “Insects do a lot of things for us in the garden that we may not realize,” says Mary Gardiner, an Ohio State entomologist and author of the book Good Garden Bugs: Everything You Need to Know about Beneficial Predatory Insects.

    These good insects not only prey on pests, but do other helpful tasks, such as pollinating and mixing compost into the soil.

    Beneficial predators include lady beetles, spiders, centipedes, lacewings, hover flies, parasitic wasps, yellowjackets, pirate bugs and damsel bugs.

    A feather-legged fly will lay eggs on squash bugs, and the larvae burrow inside the bug and eat it from the inside out. “It’s quite a dramatic death … which is quite satisfying if you have squash bugs,” Gardiner said.

    These good insects need food and shelter, Gardiner points out.

    Mulch provides some shelter, as it keeps the soil from getting too hot and drying out bugs. 

    Flowers can provide both habitat and sustenance, as pollen and nectar nourish predator insects when the bugs they eat are scarce. Good flowers for attracting insects include dill, cilantro, buckwheat, fava beans, sweet alyssum, yarrow, fennel, pansies and cosmos.  

    Gardiner warns, however, that pesticides can disturb a balanced bug ecosystem and cause outbreaks.

    “It’s really important to think about your lawn as part of your total habitat,” Gardiner says. If you spray your grass, you can harm insects that would otherwise help out in your garden.

  2. Lure pests away with "junk" food.
    Bug crawling on Egplant, The Ohio State University

    Insects have food preferences just like people, said Jim Jasinski, an Ohio State pest management researcher and extension educator. “If I put a steak in front of you and a bowl of lima bean soup, you might eat the steak first … but eventually, if you got hungry enough you might eat the lima bean soup.”

    Putting a “steak,” or diversion crop, near your cherished vegetables is known as “trap cropping.”

    Planting blue hubbard squash near summer squash or zucchini can divert cucumber beetles. Mustard or collard plants can distract flea beetles from cabbage. Eggplants can lure potato beetles away from potato and tomato plants.

    You still have to fight the pests, but the idea is to do the fighting on plants you don’t want.

    It also helps to start the trap plant early, Welty says. For example, you can sacrifice one squash plant by planting it before the others, and attack the pest insects when they show up. 

It’s really important to think about your lawn as part of your total habitat.

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Entomologist Mary Gardiner, on how weed-killers can disturb garden ecosystems
  1. Lock them out.
    Bugs on a padlock, The Ohio State University

    Row covers are made of gauze-like cloth that lets in light but keeps insects from feeding on the plant or laying their eggs.

    This method takes some effort, though: For some plants, you have to take off the covers when they need pollination. Covers can also trap heat and make plants wilt, Jasinski noted.

  2. Delay planting.
    Coming soon sign, The Ohio State University

    “Once it gets to Mother’s Day, (most gardeners) are just champing at the bit to get out there and get their garden started,” Welty said.

    Guess what? Some hungry buggers are just as eager.

    Cucumber beetles, for example, often peak around Memorial Day weekend, so if you delay your squash or zucchini until past that time, you can deprive them of their feast.

    Bennett says the potato beetle is most damaging when the plants are in bloom. You can research when the beetles come out in your state — in Ohio, it’s June — and just plant potatoes to come up later in the season.