Alternatives to pesticide use in gardens – An extensive guide

bee - Alternatives to pesticide


As part of its drinking water source protection strategy, the NFGWS has put together an extensive guide to controlling unwanted vegetation and pests without the use of harmful pesticides.

Toxic chemical sprays, such as insecticide, herbicide, fungicide and rodenticide, are used nationwide as a means of controlling unwanted vegetation and ‘pests’. Referred to collectively as ‘pesticides’, these chemicals may be effective in the short term, but target plants build up a resistance so that more chemical or stronger chemical is needed over time.

Even where they are effective, they have a detrimental impact on our natural environment (biodiversity). Herbicide spray can carry for more than 20 kilometres and there are particular difficulties where it gets into rivers and lakes. In fact, just one drop of pesticide has the potential to contaminate a waterbody such as a drinking water supply source.

Before purchasing or using such chemicals, it important to consider the fact that those plants we think of as weeds are wildflowers that have enormous biodiversity value, especially for our pollinators, including bees and butterflies.

But we know that there are many people who are not yet ready to live with weeds and want to control them. If you are one of those people, we would ask you to consider the following non-toxic methods of preventing or minimising the development of weeds and several alternative control measures where you want to get rid of them. These tips are applicable in domestic, commercial, agricultural and municipal settings.

Designing your garden/site

Tip 1: Plant as much ground as you possibly can. Don’t have a lot of empty spaces where weeds will colonise. Use mixed ground covers to blanket the bare soil that many weeds love.

Tip 2: When preparing your garden/site, do not till or cultivate too deeply as this will bring buried weed seeds up to the soil’s surface where they will quickly germinate.

Tip 3: Build competition techniques into your design, such as shading by larger plants, targeted watering etc. Similarly, organise your vegetable garden so that you have low-growing plants covering the bare soil around taller species. Layers that shade the soil make an unwelcome environment for the seed of weeds to germinate.

Tip 4: Grow a thick, healthy lawn that leaves no room for weeds, mulching in cut grass. This provides nutrients that favour grass development over weeds.

mulch - Alternatives to pesticide
Bark/mulch will suppress weed growth. However, be aware that mulching only works if done correctly (i.e. not covering actively growing weeds).

Image: Wiki Commons

Suppressing unwanted vegetation

Tip 5: Bark/mulch will suppress weed growth. However, be aware that mulching only works if done correctly (i.e. not covering actively growing weeds).

Tip 6: Tarping is a very effective control for particularly tough-to-control perennial weeds (such as dock). Strim the area all the way down to the ground, then cover it with a dark-coloured tarpaulin, completely pinning down the edges with soil. Leave the tarp in place for a year to “starve” the roots of the weeds. As this technique can negatively impact on soil organisms, it is only recommended to deal with the toughest of weeds.

Tip 7: Use newspaper as an organic suppressant tool where weeds are very prolific, or where the weed seed-bank contains a massive amount of seeds. Before spreading mulch, cover the bed with a layer of wet newspaper, ten sheets thick. Do not use the glossy inserts because the ink may contain heavy metals. Ensure the mulch you’re using over the newspaper is weed free. By the end of the growing season, the newspaper will be broken down by soil microbiology.

Alternative weed controls

Tip 8: Hoeing is an effective means of controlling weeds in their early stages of growth.

Tip 9: Pulling can be aided with tools such as weed pullers that can be operated while standing.

Tip 10: Use topping to prevent any weed seed dropping. Topping involves cutting off weed flowers and seeds before they shed. This is especially important for reducing the number of weed seeds present in the soil (i.e. the weed seed-bank).

Tip 11: Flame weeding is particularly effective for weeds growing along fence rows or in the cracks of a patio or driveway. Flame weeders are hand-held or backpack-style propane torches designed to burn the weeds with temperatures high enough to burst the plants’ cell walls. The flame can be adjusted to a very narrow, targeted range, so with care, you can even use them between rows of vegetables. Although they don’t completely kill the roots of perennial weeds, they do an excellent job eliminating annual weeds and keeping perennial types from setting seed.

Tip 12: Non-toxic chemical alternatives, such as acetic acid, are used to control unwanted plants, especially on hard surfaces. Acetic acid is a type of vinegar that is available at your local garden centre. While it kills unwanted vegetation, it is not as harmful to the bugs/insects that feed on them.

Tip 13: Boiling water/steam to kill unwanted vegetation is a very effective control for hard-to-reach places and hard surfaces. Hot foam, applied though specialist machinery, is suitable for commercial/municipal settings.

Other tips

Tip 14: If you plan to use homemade compost in your garden, make sure it is operating at temperature that weed seeds and roots are destroyed.

Tip 15: Lots of weeds come into the garden accidentally. Don’t accept plants that were dug from a friend’s garden until you make sure they don’t have a weed issue that you could end up inheriting.

hedgehog - Alternatives to pesticide
Leave bundles of small branches or a log in an area, or some bramble or leaf debris, to provide cover for hedgehogs.


Alternative ‘Pest’ controls

For the control of pests, natural predation should always be considered as the first and best option. Creating habitat for garden birds, insects and bugs will provide a cost-free and organic method of controlling pests. Provide any/all the following:

  • a garden pond (even a tiny one)
  • bird boxes and bat boxes
  • allow ivy to develop on the edge of your garden
  • leave bundles of small branches or a log in an area, or some bramble or leaf debris, to provide cover for hedgehogs

A more detailed breakdown of control methods for specific pests is provided in the table below.

Natural pest predators

Pest Predator Suitable habitat for predator/encouragement into garden
Slugs, snails, insects Hedgehogs, ducks, chickens, frogs, newts, beetles Slug pellets will kill hedgehogs, who are a natural enemy of these nematodes. To encourage hedgehogs, provide a simple wooden box as a shelter in a wild part of your garden. The entrance should be at least 13cm tall and covered with twigs/soil.

A pond is the best way to encourage amphibians in your garden. Ensure that the sides are gently sloping; ideally the pond should be over 2m wide and 60cm deep to provide the best habitat.

Ducks and hens can be kept as domestic pets that will provide eggs for your family. They will also feed on slugs, snails, and some insects. Just be sure that suitable fencing is erected.

Moths and insects Bats Bats will visit gardens with water features, hedges and night scented flowers. Bat boxes can also be installed and should be placed in a high, sheltered place but one that has access to sunlight.
Aphids/Greenfly Ladybirds Ladybirds require nectar and pollen all year round, so having the right type of flowering plants in your garden will help attract them. It’s also good to provide habitat, such as hollow holes in timber.
Snails, caterpillars, miscellaneous pests (including wireworms) Birds Provide a bird feeder and fill with a simple wheat mix. The feeder should be close to cover, high up and far away from people.
Rodents Cats, owls Rat/mice poison can be consumed by hedgehogs and other small mammals. Do not use rodenticide but look at adopting a cat/kitten to control rodent populations. Also encourage owls to frequent your garden by providing owl boxes.
ladybird - Alternatives to pesticide
Ladybirds require nectar and pollen all year round, so having the right type of flowering plants in your garden will help attract them.


Planting methods to help avoid pest damage

Crop Rotation Crop rotation is the practice of planting different kinds of vegetables in different sections of your garden each year, which helps reduce pest infestation. Some insects like to spend the winter underground and reappear in the spring to search for food. If the plant they eat has been relocated, the insect is forced to move to the source of food and is then more susceptible to being spotted by birds or other insects.
Companion planting Some plants produce a natural insect repellent, which makes them very beneficial when planted next to crops. This is known as ‘companion planting’. Planting garlic among vegetables helps to deter Japanese beetles, aphides and spider mites. Basil planted near tomatoes repels tomato hornworms, and marigolds planted with squash or cucumbers repels cucumber beetles and nematodes.

Other measures to help avoid pest damage

Beer Trap Garden pests, such as slugs, can be lured into traps. A popular example is the beer trap. This is where a jar/tin is half filled with beer and buried below the ground surface with no lid. The beer attracts insects and slugs/snails, which then become trapped.
Barriers Create a physical barrier to stop pests getting to your fruit and vegetables. One of the easiest methods is the use of a fine net. Position the net over your plants, leaving enough space for the plant to grow. By adding a cardboard collar around the stem of a plant and pressing it into the soil 2.5mm deep, some worms and other burrowing insects will be prevented from getting to your plants through the soil.

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