Get ready for the garden pests

Here’s some tips and spray recipes to help you fight back

humurous inspirational sign

Is this true or false? If you grow spuds and have pairs of barn swallows visiting or nesting in your yard, they can eat a thousand potato beetles in a few hours. I, Ted, am curious whether any Grainews reader has had such an experience. Feedback, (if any) is welcome in this connection.

Anyone who grows potatoes knows what rampant destruction potato bugs can cause. Adult beetles with voracious appetites arrive from deep within soil in late spring. They’re capable of travelling great distances on foot seeking a food source. Besides spuds, they’ll attack other nightshade family members including tomatillos and ground cherries (both in papery husks), tomatoes, peppers and eggplants. Grow all of these the farthest distance from potatoes. Tilling up soil in fall just before a hard frost brings many potato beetles to the surface; hopefully succumbing to the cold.

Occasionally I meet gardeners who tell me they’ve never had any potato beetles. Others who encounter small numbers resort to hand-picking and drowning them in soapy water and squishing egg clusters on undersides of leaves. A female potato beetle can lay a whopping 500 eggs and more.

With a tip of my hat I feel energy flow,
Headed toward the potato row,
Furrows are ready and in hand a hoe,
Planting sprouted spuds away I go.
Once potato beetles finally come,
Controlling them sure isn’t any fun,
Let’s hit these critters on the head,
Without a hammer the gardener said.

Repellent plants

Inter-plant potatoes with groups of any of these: beans, catnip, coriander, dead nettle (also known as purple archangel), garlic, ornamental garden flax, ornamental potted hot peppers, potted horseradish and insecticidal French marigold (Tagetes patula).

Beneficial insects do not resurge as quickly as pests. Welcome the good ones with annual Charmer Mix ornamental flowering flax by direct seeding some outdoors on edges and in short rows among emerging potato plants, cole crop transplants, carrots and onions. Ornamental flax creates an environment that attracts beneficial predatory and pollinating insects such as hover flies, lacewings, dragonflies and ladybug beetles.
 photo: West Coast Seeds

Annual Ornamental Charmer Mix flaxseed packets (Linum grandiflorum) come in a blend of white, salmon, pink, red and lilac colours and are available from West Coast Seeds, phone 1-888-804-8820.

The foursome of Blue Dwarf perennial border flax, (Linum perenne), insecticidal French marigold seeds (Tagetes patula), tansy seeds and dead nettle seeds are all available through Richters Herbs, phone 1-800-668-4372. Insecticidal French marigold seeds can also be purchased from Dominion Seed House, phone 1-800-784-3037.

Annual scarlet-red ornamental flax (Linum grandiflorum rubrum) is listed by Early’s Garden Centre, phone 1-800-667-1159 and Dominion Seed House (phone number above).

Gold Gem marigold (Tagetes tenuifolia) available from West Coast Seeds (phone number above) gives off an intense citrus aroma that helps confuse and drive away potato beetles. It’s quite attractive in hanging baskets and the best-tasting marigold frequently used to colour up salads, desserts and fancy drinks.

Repellent sprays and dusts

Make a foliar spray from a fish emulsion product such as liquid Organic Biofish available from West Coast Seeds at Delta, B.C., phone 1-888-804-8820 and apply to potato plants. This gives a tremendous nutritional boost and helps repel potato bugs.

Made-at-home sprays include the following: Mix one tablespoonful of hydrogen peroxide (H2O2) into four litres of water and apply directly on adult potato beetles during morning and/or evening.

Do you know a carpenter who uses cedar wood? Make a tea from a handful of cedar chips soaked in four litres of water and spray on potato foliage. In a pinch you could try soaking some clippings from pyramidal cedar tree branches instead.

Mist potato plants with water, then dust with wheat bran that has first been finely powdered in a coffee grinder or other device. Once eaten by potato bugs, they swell and explode.

Most gardeners have heard of diatomaceous earth (D E). It’s available at garden centres or farm and cattle feed supply outlets. Dust D E onto potato foliage to kill developing potato beetle larvae.

Ask a farmer who grows barley for a cup of barley kernels. Plant strips of barley seed in between potato plants and along the edges to attract huge numbers of pollinating and beneficial insects. Also, consider buying a wildflower packet of Beneficial Insect Blend seeds available from West Coast Seeds at Delta, B.C. You’ll notice an influx of predatory insects.

Make a tea from several tansy plant leaves that are steeped in four cups hot water. This can be quite an effective deterrent when misted as a foliar spray on potato plants.

Buy some essential oil of either basil, eucalyptus and peppermint or all three oils at a scoop-and-save or health food store. Add a few drops of your choice into four litres of water, then stir and mist as a foliar spray.

There’s a concoction known as giving potato bugs a dose of their own medicine made from potato beetle carcasses. Hand-pick enough as seems practical and mash up manually with an appropriate tool. Aim for a ratio of about one-third bugs covered with two-thirds volume of hot water. Steep until cool then strain off the brew and discard solid pieces. Dilute with more water if desired and apply as a spray. Apparently it infects their living relatives with a fatal virus. Don’t let any of this potato bug soup sit around as it will stink.

Research confirms what some organic gardeners have practised for years. Following tillage, a seed potato site is prepared. Place cut seed potatoes directly on the bed surface; not in the soil. The entire length and width of the bed is then covered with a foot (12 inches) of loose straw. Some compaction will result. The challenge is to maintain the same depth of straw covering throughout the growing season. That means usually adding more loose straw as often as weekly, to maintain a full 12 inches of thickness across the entire bed. It’s important the straw remains loose; not matted nor applied in mat form. As a result there are practically no potato beetles attacking growing plants while coming through the straw. ’Tis true this method may be too labour intensive for large tracts of land. The real payoff comes at harvest. It’s easy to rake off the straw and harvest mature potatoes sitting on soil surface that are easy to gather and they’re clean. Like they say when you go shopping for a new vehicle — for some it’s worth the trip.

Outdoor potato bug and insect pest spray concentrate No. 1

The story goes that potato bugs hate horseradish. One recipe calls for 10 garlic cloves and a few tablespoonfuls of horseradish brewed in two cups hot water. Once cooled, strain off liquid, discard the solid parts and add a few drops of Safer’s insecticidal soap. It’s considered better than household liquid soap as this commercial product is said to dissolve the wax-like protective coating on the outer shell of insects. Read label directions carefully when using any commercial product.

Dilute a small portion of this concentrate in a litre of plain water. Before making any large application, spray on a test site first. Plants usually show any negative reaction within 24 hours; sometimes much sooner. If too weak — add more concentrate. If too strong — use less next time.

Onion, peppermint, hot pepper, horseradish spray concentrate No. 2

This formula is also for use as an outdoor spray and may be more effective for controlling many different kinds of insect pests and potato beetles.

  • 1/4 cup hot red peppers, fresh OR dried (Wear protective gloves when handling hot peppers.)
  • 1/4 cup fresh OR dried peppermint leaves
  • 1/4 cup horseradish (OR a combo of both root and leaves is OK)
  • 1 tablespoon pure liquid household soap OR Safer’s insecticidal soap
  • 1 large onion cut into chunks
  • 1/2 cup green onion tops
  • 4 litres water

Mix hot peppers, peppermint leaves, horseradish, onion chunks and green onion tops together with two litres or enough water to cover everything. Let the mixture brew for 24 hours, then strain off the liquid and discard the solids.

Add remaining 2 litres of water and the liquid household soap OR commercial insecticide soap. You can spray this as is from a watering can with large holes on almost any plant under attack, including against potato beetles. Wear gloves and protective goggles to avoid any hot pepper mist getting into eyes. Any leftover formula keeps stable for a few days in a cool area out of bright sunlight.

A simple spray mix

This formula kills potato beetles and Japanese beetles that attack rose bushes. Mix one tablespoonful of canola oil and one tablespoonful of household liquid soap into four litres of water. An optional ingredient is the addition of one tablespoonful of rubbing alcohol. Apply from a sprayer or watering can. Remember to mist the undersides of leaves.

Bear in mind with all formulas and suggestions that you are a trial-and-error garden scientist practising at home and learning on the job. What works well for you or doesn’t work in your area may or may not work as well for others in a different part of the country.

About the author


Ted Meseyton

This is Ted Meseyton the Singing Gardener and Grow-It Poet from Portage la Prairie, Man. I salute all gardeners and farmers who help make our world a little safer and more ecologically balanced, and who toil to provide health-giving produce to others who cannot produce their own. It takes all sorts to make a world. One half of the world doesn’t know how the other half lives. The best physicians are Dr. Diet, Dr. Quiet and Dr. Merryman.



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