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In the Garden: Be prepared when insects invade

Sun., Aug. 18, 2013, midnight

This praying mantis eats a lot of insects, making it one of the good guys in the garden.
This praying mantis eats a lot of insects, making it one of the good guys in the garden.

There sure are a lot of insects out there. While some of them are the good guys, many apparently think you planted a garden just for them. What’s a gardener to do?

The most important thing is to know which insect you’re dealing with because it’d be a shame to learn later that the bug you just squashed is a voracious aphid-eater, wouldn’t it?

Refer to a garden book for insect identification or contact your local Master Gardeners as they are a good resource for ID and control ideas.

Next, attract birds to your garden. They eat a lot of insects so be sure to put out the welcome mat for them by providing food, water and shelter.

Avoid letting your plants get stressed from lack of water or crowded conditions. When this happens, research has shown plants send out an “eat me” signal to insects, which are only too happy to oblige.

Here’s what you can do if any of the following insects wreak havoc:

Aphids: Blast them off the plants with a strong jet of water from the hose. Or use an organic, insecticidal soap specifically formulated for aphids. Early in the season, cover plants that are particularly susceptible to aphids — like members of the cabbage family — with a floating row cover. This lightweight fabric lets in air, light and moisture but acts as a physical barrier to insects. You can find it at garden centers.

Cabbage loopers: These green inchworms make plant leaves look like Swiss cheese. Covering members of the cabbage family with a floating row cover at the beginning of the season prevents cabbage butterflies from laying eggs on the leaves. Another option is to use an organic product called Bacillus thuringiensis (Bt). It contains bacteria lethal to the larval (caterpillar) stage of insects but is harmless to humans.

Cutworms: If your seedlings are chewed off at ground level, these chubby gray worms are to blame. Try sprinkling the soil around the plant stems with diatomaceous earth. This flour-like substance contains the fossils of ground-up crustacea; its sharp edges will cut into the worm’s skin, causing it to dehydrate and die. Next year when planting tender seedlings like corn, tomatoes or peppers, surround the stems with a paper collar that has been sunk halfway into the ground to keep them away.

Earwigs: Place small sheets of damp cardboard onto the soil surface late in the day. The earwigs will hide in the cardboard. Pick it up in the morning and dispose of it.

Leaf miners: They damage the leaves of Swiss chard, spinach and beets. The adult fly lays eggs on the leaves. The maggots tunnel within the leaves and cause plenty of damage. I cover my susceptible plants with a floating row cover for the entire season to keep the flies away.

Slugs: Diatomaceous earth works well or use organic slug baits. You can also sink a small container of beer into the soil, with the lip of the container at the soil surface. Slugs are attracted to the yeast in the beer, fall into the container and drown.

Tomato hornworms: These huge green worms eat the leaves and fruit of tomato plants. Either handpick them from the plants or spray them with Bt.

Susan Mulvihill can be reached via e-mail at Visit her blog at for more gardening information, tips and events.

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