Mar. 15 column: Beneficial insects

Beneficial insects

Here is a link to my column in today’s edition of The Spokesman-Review: Welcoming good bugs will help oust pests. (you can read my column lower in this post.) Today’s topic is about attracting beneficial insects to your garden. For years, I’ve prided myself on growing everything organically. When I occasionally have insect problems, one of the things I’ve used is an organic spray.

After reading “Attracting Beneficial Bugs to Your Garden” by Jessica Walliser, I am completely rethinking my strategy. (note: you can read my review of her book on this blog)

Walliser explains that beneficial insects are more affected by organic sprays. That in turn throws off the populations of good bugs vs. bad bugs. If you knock off the good guys, other types of pest insects can have a population surge. You definitely don’t want that!

She recommends letting nature find its balance in your garden. Walliser suggests attracting beneficial insects so they can help us deal with any pest insects. Fair enough.

I hope you’ll find the column interesting. I’ve included a list of plants that Walliser recommends so you can plan ahead. I intend to dedicate more areas of my garden to these plants. I’ll report back on occasion to let you know how it’s going.

Beneficial Insects garden column:

by Susan Mulvihill

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. 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. That’s because you’ve taken away a primary food source for beneficial insects.

Do you have aphids, hornworms, Colorado potato beetles, leafhoppers, cabbage worms, thrips, scale or mites? They are preyed upon by beneficial insects. Examples include ladybugs, beetles, lacewings, hover flies, praying mantids, 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 guys. Walliser’s book has useful photos and there are other excellent insect guides to assist us with this as well.

A valuable local 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. The clinic is located 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 in my vegetable garden that should be in all organic vegetable gardeners’ arsenals. That is floating row cover. This lightweight fabric lets in light and moisture. But it 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. Those are cabbage family crops (aphids and green inchworms) and spinach, Swiss chard and beets. The latter group can be plagued by leaf miners.

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 non-native insects such as codling moths and some stink bugs is a different matter altogether. I’ll address that in a future column.

Flowers that attract beneficial insects

  • Angelica species
  • Aster, hardy (Symphyotrichum)
  • Basket of Gold (Aurinia saxatilis)
  • Black-eyed Susan (Rudbeckia species)
  • Bolton’s aster (Boltonia asteroides)
  • Coriander (Coriandrum sativum)
  • Cosmos (Cosmos bipinnatus)
  • Culver’s root (Veronicastrum species)
  • Dill (Anethum graveolens)
  • Feverfew (Tanacetum parthenium)
  • Golden marguerite (Anthemis tinctoria)
  • Goldenrod (Solidago species)
  • Lovage (Levisticum officinale)
  • Oregano (Origanum vulgare)
  • Shasta daisy (Leucanthemum x superbum)
  • Sunflower, common (Helianthus annuus)
  • Sunflower, false (Heliopsis helianthoides)
  • Sweet Alyssum (Lobularia maritima)
  • Tickseed (Coreopsis species)
  • Wallflower (Erysimum species)
  • Yarrow (Achillea millefolium)