BLOG: Natural Pest Control

Workshop Series: Natural Pest Control

Missed the workshop but still interested in learning how to manage some common garden pests without chemicals? Keep reading to find out what you can do to achieve this in your own green spaces.

Why be pesticide free? Pesticides are agricultural chemicals that are used to control pests (such as weeds, insects, and disease) on food crops and ornamental plants. Garden centers are the place to go when considering your chemical pest control options, but for more on chemical free gardening, keep on reading as we discuss some common pests & natural strategies.

Before we get into the specifics, let’s address the natural pest control toolbox.

·         Nematodes / soil microorganisms

o   Can be purchased from garden centres, these microorganisms are soil warriors and a great example of why we don’t want to apply pesticides to our soils.

·         Beneficial insects

o   Insects aren’t all bad. Some garden insects such as ladybugs and lacewings consume aphids and other pest species so you don’t have to.

·         Mulches

o   Mulch is any kind of soil cover with benefits like water retention, weed control and erosion control. However, natural mulches like bark provide a habitat fr many beneficial insects.

·         Water regimes

o   Consider when you water and how you water. Water can be a vector for disease if it touches an infected plant and drips on to uninfected surfaces.

·         Crop rotation

o   Crop rotation is commonly forgotten in backyard gardening, but following a standard 4-year rotation can keep pest populations low and your soils healthy.



Tent Caterpillars

These caterpillars are a common pest in recent years but don’t worry, their population numbers are decreasing once again. This caterpillar has an outbreak every 8-10 years & lasting 2-3. The caterpillars feed for approximately 6 weeks before going through metamorphosis and becoming a moth. The moths lay egg bands on the branches of food sources to overwinter and hatch the following spring.  


Predators include birds, bats, mice, frogs, skunks, other insects and a variety of parasites


·         Preventative – remove egg bands between late summer/early spring by cutting it off a branch using a small knife or box cutter.

·         Hand picking/physically removing from plants

·         BT (will kill any soft bodied insects, such as beneficial butterflies)

·         Keep the tree healthy by keeping it well watered and avoid fertilization during the caterpillar feeding period

Typical food plants: trees and shrubs, but aspen is a favorite. They also feed on oak, basswood, ash, poplar, cherry, plum, raspberry and many other plants.



Figure 1 - Forest Tent Caterpillar (Copyright © 2013 Amy Goodman -


Flea Beetles

This pest is typically found on vegetable plants, causing damage by eating the leaves, especially the young foliage.


Typical food plants: Vegetables (mostly brassicas, but also some other veggies and some weeds)


·         Preventative – Floating row cover

·         Late planting to avoid egg laying period


Figure 2 - Flea Beetle (Copyright © 2014 Tom Murray -


Cut Worms

The icky little grubs are nocturnal feeders that cut the stems of plants right off.

Typical food plants: Vegetables and herbaceous fruits (ex. strawberry)


·         Preventative – place collars around plants, 2” deep into the soil (ex. toilet paper tubes, aluminum foil or other available materials)

·         Hand picking at night (they are nocturnal)

·         Disturb the top 1”-2” of soil during the day and remove any found in the soil

·         Remove plant debris at the end of the season, till top 3” of soil to destroy remaining eggs if infestation was particularly bad


Figure 3 - Cut Worm (Copyright © 2013 Vinny -


Root Maggots

Root maggots pose a risk much higher in Saskatchewan due to the large canola industry. These flies love brassicas (such as canola) and thrive in our province.

Typical food plants: brassica vegetables (ex. radish, broccoli, kale, cabbage, etc.)


·         Preventative – Till soil 2-3” in spring to destroy overwintered eggs

·         Preventative – Use floating row cover

·         Mulch around your plants, a thick layer of mulch is a good habitat for predatory beetles

·         Plant garlic around your important brassica crops to help keep the root maggots away


Figure 4 - Root Maggot (Copyright © 2016 -


Cabbage Moths

Also known as cabbage loopers and common white butterflies, these little green caterpillars are bad for damaging brassica crops in the summer.

Typical food plants: brassica vegetables (ex. radish, broccoli, kale, cabbage, etc.)


·         Preventative – floating row cover

·         BT (will kill any soft bodied insects, such as beneficial butterflies)

·         Removing eggs by hand (or removing leaves with eggs attached, eggs are yellow and can be found on the underside of leaves)

Figure 5 - Cabbage Looper (Copyright © 2012 -


Powdery Mildew

A white, dusty film on leaf & fruit surfaces. Caused by humidity & cool, damp weather conditions, this disorder is not life threatening to plants and does not drastically change the quality of your produce. However, this disorder can slow the growth & development of your crop. Typically found on cucurbits (pumpkin, squash, cucumbers, etc.)


  • Preventative – avoid watering the leaves of the plants at night or on cool, humid days (moisture control)
  • Preventative – copper sulfate spray (not organic, but not a hazardous chemical), this does not affect the disorder after it appears on the leaf surface.


Figure 6 - Powdery Mildew (Copyright © 2009 -


Late Blight

This disease can wreak havoc on backyard gardens as well as commercial fields. Late blight attacks solanaceous vegetables (ex. potatoes, tomatoes, peppers, eggplants, etc.) only and is not the same as Early Blight.

Symptoms include:

  • Lesions on older leaves following several days of warm, wet or humid weather 
  • Lesions begin as dark green, water-soaked areas at the leaf tip, a yellowish-white halo will often surround these lesions (these lesions can spread beyond the leaf veins & leaf)
  • A white fungal growth can sometimes be detected on the underside of infected leaves, especially on dewy mornings
  • Sunken lesions around potato eyes that are sometimes reddish in colour


  •  Do not plant potatoes from an infected plant or field
  •   Potatoes that have been infected must be removed and buried apart from your garden space (keep spores from spreading)
  • Foliar copper sprays can be utilized to prevent & control the spread of late blight, but must be reapplied immediately after rains (or overhead irrigation)

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