In the Garden: Welcoming good bugs will help oust pests

How do you approach insect control in your garden? Recently, I read a book that has me rethinking what I have been doing for years.

In “Attracting Beneficial Bugs to Your Garden” (Timber Press, 240 pp., $24.95), author Jessica Walliser makes convincing arguments for ditching the organic sprays and letting beneficial insects prey upon the harmful ones.

“It’s a shame, really, that we focus so much on the so-called bad bugs, spending hours and dollars battling them,” she writes. “If we could all manage to switch our focus to encouraging the good bugs, we would allow our gardens to return to a natural balance, giving the control of the garden back to the insect world.”

I’ve long figured that using organic pesticides to control insects was perfectly fine because I wasn’t using harmful chemicals. But as Walliser explains, pest insects can become resistant to them. What’s more, beneficial insects can be more affected by organic sprays than the pest insects we’re targeting. That can cause an increase in the population of other troublesome insects and suddenly you’ve got more problems than what you started with.

A similar problem occurs if you wipe out a bunch of the bad bugs, because you’ve taken away a primary food source for beneficial insects.

Aphids, hornworms, Colorado potato beetles, leafhoppers, cabbage worms, thrips, scale and mites are preyed upon by beneficials such as ladybugs, beetles, lacewings, hover flies, praying mantises, parasitic wasps, dragonflies and spiders.

What’s a gardener to do? There are two important steps we should take:

First, be familiar with the insects in our gardens. It is essential that we learn to differentiate the good guys from the bad. Walliser’s book has useful photos and there are other excellent insect guides to assist us with this as well.

A valuable resource for Inland Northwest gardeners is the WSU/Spokane County Master Gardener plant clinic. Clients can bring in insects they have frozen ahead of time for identification in the clinic, which is at 222 N. Havana St. They can also call (509) 477-2181 for guidance or email insect photos to mastergardener@spokanecounty.org.

Second, attract beneficial insects. How? If we plant flowers that provide food and shelter, beneficials will grow, reproduce and dispatch pest insects. Refer to the plant list for Walliser’s suggestions.

There is one product I use that should be in all organic vegetable gardeners’ arsenals: floating row cover. This lightweight fabric lets in light and moisture but acts as a physical barrier to pest insects when draped over plants that need protecting.

There are only a few vegetable crops that can have problems: members of the cabbage family – which often attract aphids and green inchworms – and spinach, Swiss chard and beets, which can be plagued by leaf miners.

Since none of these crops needs to be pollinated, cover them at planting time and pest insects will be none the wiser about what’s growing underneath.

Dealing with nonnative insects such as codling moths and some stink bugs is a different matter altogether, which I will address in a future column.