Organic pest control

Get on top of your pests without using chemicals.

 ‘How could we have ever believed it was a good idea to grow our food with poisons’? Dr Jane Goodall

Many gardeners have good intentions of growing their plants without using dangerous chemicals, but when their favourite rose bush or ripening tomatoes are attacked by a plague of pestilence, they buy an armoury of pesticides and attack the offending insects or fungi with anything they can. It is, however, completely possible to control any pest using organic methods.

Changing the way we think of pests

Don’t jump at every insect you see with your spray bottle and swatting slop. Many insects actually help to control pests like predatory beetles, praying mantis, parasitic wasps and ladybugs, to name a few. Before you kill something, watch it for a while and establish what it’s feeding on: your plants or another insect?

Mealie bugs

These fluffy little insects do suck the sap from plant stems but they’re not pests in the traditional sense. They only occur on unhealthy plants and are great big signposts that tell you to leap into action. Check for the following:

  • Is your plant malnourished? Feed with organic fertiliser and compost. Use worm tea for an extra boost.
  • Does your plant need pruning?



Crickets in your lawn are also a cry for help. Crickets can coexist with your plants happily when they live in flowerbeds. They will only venture into the lawn and cause damage and unsightly tunnels if the soil is hard; hard soil under your lawn is caused by a lack of organic matter and an absence of earthworms and beneficial soil fungi. The two main causes of this are:

  1. Using chemical fertilisers, pesticides and herbicides.
  2. Applying tobacco scrap to the lawn.



While we might not enjoy grasshoppers chomping our veggies or roses, they are not pests in all areas of the garden. The growth of some shrubs, particularly indigenous ones like the Buddleia species, is actually stimulated by grasshopper grazing.

Three steps to growing healthier plants organically

 Prevention is better than cure; keep your plants healthy by:

  1. Feeding them regularly with organic fertiliser and compost so that they are more resistant to pests.
  2. Plant companion plants.
    • Garlic, rosemary, lavender, wormwood, pennyroyal and catnip help to ward off mites, aphids and fungal diseases.
    • Sage, comfrey and chamomile are also great companion plants that boost general nutrient absorption and plant health.
  3. Cultivate a biodiverse, healthy ecosystem in your garden.
  • Earthworms turn over and soften the soil and move organic matter downward; their castings provide vital plant nutrients.
  • Beneficial soil fungi and mycorrhizae form a network that moves nutrients and water through the soil to your plant’s roots. Some of them also directly impart disease resistance to your plants. Killing these fungi by spraying your plants with chemical fungicides ironically makes your plants more susceptible to the diseases and pests you are trying to eliminate.
  • If you include dense shrubs and trees for birds to nest in, as well as some indigenous fruit and seed plants and bird baths in your garden, then you’ll encourage a healthy population of birds that will keep your insect pests in check.
  • Keep guinea fowl or bantam chickens in the garden to control termites, crickets, cutworm and other pests.

Your soil is your foundation! It is impossible to achieve a healthy pest-free garden without investing in your soil.

Organic control techniques and methods

Route 1: Buy organic pesticides

Many of the leading nurseries around Harare stock a range of organic pesticides, such as Levo, that are as effective as chemical alternatives.

Route 2: Make your own

Homemade pesticides must be made fresh each time. Just remember not to water for 12 hours after spraying.

A general pest spray for aphids, mites, scale and fungal diseases

  • Fill a large jug to at least half way with the leaves of wormwood, lavender, catnip and pennyroyal.
  • Fill the jug with boiling water and cover to stop the volatile oils from evaporating.
  • Steep for a few hours until cool.
  • Strain to remove the solids and use them as mulch under your roses.
  • Retain the liquid and decant into a garden spray bottle and use as a general pest spray every three to four days on affected plants.


Powdery mildew

  • Add two heaped tablespoons of bicarbonate of soda to a litre of water.
  • Spray on the leaves, flower buds and stems of your plants that are infected with powdery mildew.
  • Apply every three days until all signs of mildew have disappeared.


Slugs and snails

  • Submerge a dish, less than 2cm deep, so the rim is level with the ground and fill with water, 1 tablespoon yeast and 1 tablespoon of sugar. Attracted slugs and snails will drown.


Black ants

Mix icing sugar and bicarbonate of soda (1:1) and place in a thin line or small pile near the affected area. The ants will eat the mixture and carry it back to the nest for their young. All the ants that eat it will die from the gas produced when the bicarb reacts with the formic acid in their stomach.

Demystifying the myths

Myth 1: Marigolds are good for deterring pests and nematodes

Recent research has shown that living marigolds have little to no deterring effect on pests or certain nematodes and, in fact, roses, spinach and tomatoes are more susceptible to red spider mite when planted near marigolds. If you want to use them, bury the shredded dead plants into the soil of your vegetable garden. As they breakdown they will release alpha-terthienyl, a gas that is toxic to certain nematodes.

Myth 2: Sunlight liquid is good for getting rid of crickets, aphids, etc.

Sunlight liquid is a chemical soap. It can cause sunburn on your plants, block the stomata that leaves use to breathe and damages your earthworms and soil fungi.

Top Tip: If you decide to ‘go organic’, make sure that the products you choose to use are not harmful to the people, pets, beneficial insects, worms and microbes that you do want in your garden. Some organic options are toxic.

 By Lindsay Charters

For a full guide to organic garden feeding and pest control, please visit


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