Natural Insect Control In The Garden

The majority of insects you find in your garden are actually harmless and require no intervention. They are either nature’s helpers or food sources for nature’s helpers. For those insects that do pose a threat to some of your plants there are several non-invasive solutions you can utilize to prevent, monitor and control these pest insects.

This approach to pest management is called IPM or integrated pest management. Their premise is simple, begin with the least invasive and most environmentally sound treatments, gradually working your way up to the more invasive treatments (only if it becomes necessary).

The Benefits of This Type of Response to Pest Insects Includes:

  • Sustaining a healthy population of friendly insects that will serve to help keep the bad ones under control.
  • You will attract more pollinators to your garden thus producing more blooms, fruits and vegetables.
  • You be able to maintain a healthy soil microbial population, translating into healthier more disease resistant plants.
  • Garden edibles will taste better and be safer for your consumption.
  • You will also have fewer problems in the long run, as Mother Nature will perform much of the work for you.

The First Step of Integrated Pest Management is Prevention:

Your best line of defence is a good offence. Doing what can be done to prevent insect problems just makes good sense and it will save you both time and money in the long run. Some examples include:

  • Planting pest-resistant varieties where the pest is a problem.
  • Companion planting: By planting specific companions for your plants you may be able to help ward off insect attacks. Other benefits include improving the plants health and/or enhancing its flavour. There are several good books on the subject. (A couple that come to mind are ‘Roses Love Garlic’ and ‘Carrots love Tomatoes’.)
  • Time you’re planting around insect hatchings: Some garden plants may be able to be planted after a particular problematic pest has run its course. If you have a problem with leaf-miners try planting susceptible plants from early June onward.
  • Eliminate structural conditions that encourage pests.
  • Attract Beneficial Insects (like lady bugs, lace wings, parasitic wasps, tachinidad flies and praying mantis to your garden. You need these insects to control the pest insects and to pollinate your plants.
  • Draw on the services of other  mother nature’s helpers: Like birds, toads, bats and nematodes.
  • Practicing good sanitation: While some garden debris is beneficial for adding organic matter to the soil and many insects prefer to munch on fallen debris over your plants; too much of a good thing becomes a bad thing. Too much debris invites pest insects and also provides a breeding ground for both insects and disease.
  • Create physical barriers:
    1. Place toilet paper rolls or paper towel rolls around new seedlings and insert them 1″ into the soil, to protect against cut worms.
    2. Place floating row covers over spring vegetable crops.
    3. Install netting over a fruit trees and berry crops, to protect them from the birds.
    4. Install grease bands around the trunks of fruit trees (especially apple, plum, cherry &pear trees) to help prevent the females of certain wingless moths from climbing up the trunks to lay eggs.
    5. Place sticky bands around the trunks of fruit trees to control ants that guard aphid colonies.
  • Control Weeds: Many insects (both beneficial and pest) are attracted to weeds. Either as a source of food or a place to lay their eggs. Get to know your weeds and keep the bad ones pulled.
  • Choose natural fertilizers over chemicals: Chemicals upset the soil organisms that are instrumental in helping to control many pest insects.
  • Keep a healthy garden: Insects tend to attack weak, sickly and stressed plants first.
  • Water regularly, so plants aren’t stressed by drought.
  • Stake plants to keep them off the ground and dry.
  • Mulch to prevent soil and pathogens from splashing onto the plant.
  • Rotate your crops so that over-wintering pest insects will lose their food source and die off.
  • Remove and dispose of diseased or infested plants.

Monitoring

Once you have taken the precautions you can to prevent pest insect outbreaks the next step is to monitor your garden and be on the lookout for potential problems. 

  • Yellow sticky tapes can be used to help keep an eye on insect types and populations.
  • Monitor your plants regularly. Watch for the first signs of garden pests, like holes, wilting, webs and color changes. Check the undersides of leaves. Check the branches. Look for eggs and nests.

Treatments

Identify the problem before treating it. Determine if it is just an isolated incident or a full blown attack. Is the pest still present or has it already been and gone. Once you have identified the pest and determined whether it warrants intervention following are a few natural treatments available to you.

Dormant oils: (Used for over wintering stages of mites, scales, aphids, and other insects). The primary way horticultural oil kills insects is by suffocating them. The oil blocks the spiracles through which insects breathe. Horticultural  oils also disrupt the metabolism of insect eggs and the ability of some insects to feed, causing them to starve to death. The temperature must be above 5 degrees C. (Caution: some plants are sensitive to this oil, like Japanese maples and blue spruce. Test an area on a plant first, and remember to spray before bud break.)

Diatomaceous earth: is made of finely ground skeletons of small, one-celled creatures called diatoms. They are an effective treatment for slugs and other soft bodied insects.

Physical controls:

  • Hand picking works well for some of the larger, slower insects like: (slugs, snails, caterpillars, lily beetles and other pest beetles like June, Japanese and Viburnum leaf beetles) Drop the insects into a bucket of warm soapy water.
  • Use a cue tip or cotton swab dipped in rubbing alcohol to remove pests like scale and mealybugs.
  • Remove and destroy pest insect eggs sacks and nests.
  • Hand squash aphids or blast them with the garden hose, careful not to damage your plants in the process.

Insecticidal soap: Useful against small soft-bodied insects such as aphids, mealybugs (crawler stage), spider mites, thrips, and whiteflies. This soaps active ingredients are potassium salts of fatty acids.  It works in 2 ways.  It penetrates the insects cuticles, causing cellular collapse and desiccation. The oil content also serves to suffocate the insects.  Direct contact must be made with the best in order for it to be effective. Some plants such as ferns, mountain ash, nasturtiums or Japanese maples may be damaged by the soap. It is always a good idea to test a small area first. Also note they should not be sprayed on hot days. Multiple applications are usually required.

BT (Bacillus thuringiensis) a soil-dwelling bacterium, commonly used as a biological pesticide. It is available in either a liquid spray or as a dust. It is an effective treatment against caterpillar infestations. When ingested by a caterpillar, the toxin affects it’s digestive tract, causing it to quit feeding and die in a few days. Be careful when spraying and wear a mask.

Garden Sulphur: Effective for use as a fungicide. It can be used to treat powdery mildew, rust, black spot, scab, mites. Can be used as a powder or a spray. Do not apply when hot. Some plants such as grapes, apple, pear, blueberry, currants, gooseberry, apricot, vines are sensitive to sulphur.  Be sure to test an area first. 

Neem Oil Products: Is a broad-spectrum insect poison, repellent, and feeding deterrent. It also stops or disrupts insect growth and sterilizes some species. It appears to be easy on beneficials and of low toxicity to mammals. Can be used as an insecticide or  fungicide. Dilute and apply as per manufactures instructions. (Full spectrum neem oil products will offer some systemic action.)

Homemade Insecticides: There are many home made and natural recipes circulating out there. Check out the internet, especially the horticultural departments of some universities, organic gardening sites and of course your local Master Gardeners. You will find recipes for treating common problems such as black spot, powdery mildew, aphids and slugs, as well as recipes for general fungicides, miticides and pesticides.

Cornell University Formula: (fungicide, miticide, or pesticide)

Basic ingredients:

  • 2 tablespoons fine horticultural oil
  • 1 tablespoon mild liquid dish soap (not detergent)
  • 1 heaping tablespoon baking soda
  • 1 gallon (4.5L) of water

Optional ingredients:

  • 1 tablespoon or the equivalent of 8-8-8 fish emulsion/liquid seaweed (make sure your product does not contain sulphur)
  • 5-7 droplets of a liquid plant vitamin mixture
  • Bacillus thuringiensis var. Kurstaki (Bt), at the recommended concentration (controls caterpillars).

This is a contact spray and the insect must be present at the time of spraying. Spray every two weeks if the pest insect is still present.

Other treatments and interventions available to the home gardener include:

  • Sticky bands: (Late April-early May)
  • Wrap your tree trunk with 2 widths of duct tape at about chest height from the ground. Then carefully smear Tanglefoot around the center of the duct tape. The caterpillars will stick to the tangle foot and you can pick them of and destroy them.
  • Burlap cloth bands: (Late May-August) Wrap a 3m band of burlap around the tree trunk. Tie it in the middle with a rope and fold the top ½ down. Caterpillars feed at night and hide during the day in shelters that protect them from the heat. They will congregate under the burlap. Destroy caterpillars that emerge from under the burlap late in the afternoon before they crawl back to the canopy to feed. They crawl down the tree in the early morning and look for a place to hide.
  • Natural predators: Blue jay, blackbird, catbird, black-capped chickadee, crow, grackle, red-winged blackbird, nuthatch, oriole, chipping sparrow, robin, tanager and woodpecker.

Photo Credits: all photos taken by the author.

All rights reserved

Terms of use: photos and content may be used for non-profit use and education with proper attribution and link back to page found.

For photos: Kimberley Pacholko Natural Insect Control In The Garden – Horticulture For Home Gardeners

For content: Kimberley Pacholko 2021, Ornamental Garden Specialist, Natural Insect Control In The Garden – Horticulture For Home Gardeners

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