News for those who live, work and play in the Santiam Canyon

Pests can be natural enemies of your garden

Linn County Master Gardener

OSU Linn County Master Gardener.

What’s eating my plant? Will the plant die? Is the fruit still edible? How do I make the insect go away without chemicals? The possibilities for bad bugs is endless. 

Often specific insects are attracted to specific plants, like root weevils notching rhododendron leaves. We recognize most of the common pests in the garden, but with hotter, dryer summers, new insects will be migrating to our more pleasant climate. 

There are some simple things we can do to reduce the appeal of our plants to insects and to interrupt their cycles. How you react to pest problems depends on how much you  value the crop, how much it will cost to fix the pest, and your feelings about pesticides.

Integrated Pest Management (IPM) is an approach to maintenance in the garden that will predict and prevent pest activity before it becomes intolerable. 

The most important approach is to grow healthy plants. Provide adequate sunlight, water, air circulation, and soil nutrients so the plants can build up their own defenses and stay strong even with a minor pest attack. Pests usually seek out weak, stressed or decaying plant matter. 

Choosing disease-resistant varieties, especially if the crops are not rotated or moved every year or two, will make it harder for pests and diseases to get established and stay on. 

IPM includes regular inspection of plants and garden conditions, making note of any damages, changes, and cleanup that need to be done to prevent problems. 

Sometimes it means walking around with a bucket of soapy water and gloves, picking off the unwanted intruders and dropping them into the toxic bubble bath for disposal later. 

A children’s butterfly net is useful for catching grasshoppers and other elusive hoppers or movers in the garden. 

Checking plants several times a week and at different times of the day can catch problems before they get out of control. Look at the undersides of leaves where insects often hide. Scratch around the soil at the base of an affected plant to look for larvae or eggs.    

Before blaming the bugs, consider other causes of the problem. Has the plant been overwatered or just planted in the wrong spot? Does the sprinkler miss that spot? Has a neighbor been spraying weed killer when the wind blew? Is a shrub or tree suffering from lawn mower blight (impact). Did a dog or cat “overfertilize” there? What else could be happening? 

Remember that not all bugs are bad. Most insects are harmless, helpful, and even prey on other insects. Provide a habitat for beneficial insects, like blooming flowers and coarse mulch. 

Some beneficial insects are the minute pirate bug, western damsel bug, lady bug, and green lacewing. Centipedes and big black beetles are helpful, too. Those black beetles prey on smaller insects and small slugs, so stop stepping on them. 

Ants will “farm” aphids to steal their sweet sticky excrement, and will even defend the aphids from attackers. If you see such activity where the aphids are sucking the life out of plants, wash the aphids off with a strong spray of water and deal with the ants. 

Some plants do not get along with one another. Some “companion” plants actually attract or repel certain insects. 

Nasturtiums, for example, attract cucumber beetles and other undesirable plants away from the crop, but when the nasturtium gets infected it may have to be tossed, bugs and all. Marigolds and onions are famous for deterring pests because of their chemical “stink.”

What is your tolerance level for how much damage you can live with? Sometimes the leaves of a plant get holes in them, but the flowers and fruit are not affected. 

If insect bites cause the fruit to be blemished or misshapen, use the produce in a way that no one will notice – chopped, sliced, cooked or however improves the appearance before eating. 

If the pest has done its damage and gone, the produce or flowers may still be useful but without the protein. Some retailers actually sell misshapen fruits and vegetables at a slightly lower price, making them a bargain.

Try prevention, physical controls and biological controls first. Hand picking, clipping clusters of insects with pruners, hanging netting or covers over the plants, chicken wire or fencing to keep animals out, frequent cultivation of the soil, or whatever creative solutions you can come up might control the problem. 

Biological controls like beneficial insects, birds and bats, snakes, or companion planting might help. If a pesticide seems necessary, choose a chemical that is least toxic to you, most specific to the pest you are targeting, and least harmful to the environment. 

Some organic options include insecticidal soap, neem oil, iron phosphate granules (for slugs), traps, and other products at garden centers. 

If you can’t identify what the pest is, try asking your phone “what are pests on … ?” You might even get a picture to match it. 

If you take a picture of the problem, you can email it to “Ask an Expert” at or show it to a Master Gardener at an extension office or community event. 

There is EC1613-E, A Pocket Guide to Common Natural Enemies of Crop and Garden Pests in the Pacific Northwest available from OSU Extension at _natural_enemies.pdf if you want to attract or encourage bugs that eat other bugs.

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