Natural Pest and Disease Control

How to Manage Pests Naturally

Natural pest control may not be as complete as using toxic chemicals, but if used regularly it can have a big impact and normally keep serious pest outbreaks from occurring.

There are three cornerstones to Natural Pest Control:

Ensure that plants are as healthy as possible

Create conditions that discourage pest and disease organisms

Isolate any pest or disease infections

How to Keep Plants Healthy
There are two ways to keep plants healthy so that they are more resistant to pests and disease.
1. Select resistant plants, and
2. Provide plants with the best conditions for healthy growth.
Some plants will naturally have fewer problems with pests and diseases than other plants.
Most plants, however, will have problems with pests and diseases at some stage.
How many problems they do have will be influenced by where the plant is grown and by climatic changes throughout the year. For example:

For vegetables and annual flowers, those planted early in the season have less chance of having heavy infections than those planted late in the season.

For other plants, get to know your immediate locality and the plant varieties that grow there. Look around your neighbourhood and take note of plants that have fewer pests or diseases. Talk to your local nurseryman and other gardeners.


Create optimum conditions for your plants

It is important to appreciate the difference between optimum and tolerated conditions. If the soil moisture, air temperature, nutrient (fertiliser) levels, and other conditions are at an optimum level, the plant will be its healthiest, and more able to fight off infections.

When conditions are either side of optimum, any plant (even hardy species), will be weakened. In these conditions, damage from pests or diseases can be more significant.

This means that you need to avoid extremes. For example,


Too hot can be just as bad as too cold.



Too wet can be just as bad as too dry.



Too much fertilizer can be just as bad as too little.


Some of the more pest and/or disease resistant varieties of vegetables available include:




Chilli Pepper






Gourmet's Delight, Pioneer, Brown Beauty


Isolating Pest or Disease Infections

Pests and diseases will always spread from plant to plant, so to reduce the chance of healthy plants becoming infected, keep any diseased plants away, following these guidelines:


When you see an infected potted plant; move it away from your other plants.



Use barriers to keep pests off plants wherever you can (eg. Netting can keep some pests away.)



If you are growing plants that are very different to plants grown by neighbours that are susceptible to disease, you are less likely to find that diseases attacking those species will affect your plants.



If you find that part of a plant is infected, remove the infection and destroy it before it can spread.



Reduce the Spread of Pests and Diseases

There are three ways that you can reduce the spread of pests and disease: You can deter pests and disease through practical measures, you can kill the pests or disease directly with sprays and dusts, or you can make use of biological controls.


Deterring Pests and Diseases

The use of a range of practical insect controls will deter pests and diseases. The key is to use the appropriate method at the appropriate time. Some specific examples include:

Using traps to attract insects. For example, many types of insects tend to be attracted to the colour yellow. Strips of yellow plastic coated with a sticky substance can be used to attract and catch insects like aphis.

Banding the trunk of a tree with a sticky layer to prevent and trap insect larvae crawling up into the tree (e.g. codling moth).

Creating dusty furrows around plants which discourage the movement of chinch bugs.

Irrigating an area heavily, which will kill off insect populations (perhaps consider flood irrigating if soil insects are a problem).

Draping young trees with a covering of cheesecloth which will discourage cicadas.

Wrapping the trunks of transplanted trees which can prevent some types of borer attack.

Placing paper or plastic collars around a plant to discourage movement of cutworms.

Using tree wound paints to provide a barrier to wood borers and some types of ants.

Using companion planting to deter some plant diseases. For example, garlic planted under a peach tree will improve the performance of the peach by deterring the development of peach leaf curl, a common disease on peaches.



Killing Pests and Diseases

There are a growing range of naturally derived sprays and dusts that can be used to effectively control a wide variety of pests and diseases.

Natural poisons for controlling various pest and disease problems include:

Soapy water

Diatomaceous earth



Sulphur oils

A classic, environmentally friendly way of killing insects is to spray them with a film of oil, which will suffocate them. Insects breathe through their skin, so coating them with oil can stop them breathing. The trick is to use the right type of oil, as spraying will coat the surface of the plant with oil and some oils can cause damage to plants. A coating of oil on a very hot day can also cause sunburn on a plant. Extracts or oils from the following will also repel a variety of different insect pests: peppermint, garlic, eucalyptus, lavender, rue, wormwood, elder, hot chillies, pennyroyal, melia azedarach and tobacco.


Using Biological Controls

Biological control is the use of a biologically derived agent (i.e. plant, insect or animal) to control pests and diseases. This commonly involves the use of diseases that affect the pest or weed (the disease might be spread by an insect), the use of predators which eat pest species, or beneficial insects which either eat or parasitise the pest.



Caterpillars are successfully controlled by 'Dipel', a commercially available bacteria which is sprayed onto the plants. Caterpillars eat the bacteria and later die. Pests themselves can be collected, squashed and a spray made from them. This will hopefully spread any parasites and diseases around to infect and kill the pests.



It is important to have natural predators in a garden to keep pest numbers down. Examples include lizards, frogs, dragonflies, spiders, and birds. To be effective, these predators need places to shelter and breed (e.g. hollow logs), food (insects, nectar, pollen) and water. Insect eating birds can be attracted into the garden with native plants like gums, grevilleas and bottlebrushes.

Many insects are also good predators of pests, including:

Ladybird beetles and their larvae, which eat aphids.

Hover flies (Syrphid flies), which eat aphids.

Lacewing, which will control mites, caterpillars, aphids, thrips, mealybugs and some scales.

Predatory mites, which eat other pest mites.

Praying mantis eats most other insects, pests or otherwise.



Helpful parasites in pest control include:

Wasps, which attack many types of insects including caterpillars. Plants such as chamomile, celery, hyssop, tansy, dill, and yarrow will attract wasps to the garden.

Woolly aphis parasites are attracted by clover (Trifolium sp.).

Lacewings, which feed on aphis and other insects, are attracted by sunflowers.

Goldenrod (Solidago sp.) attracts preying mantis and other predators.


Plant Sprays for General Pest and Disease Control


Extract from

How to Apply it


Chrysanthemum coccineum




Most insects




Some fungal diseases many insects





Many insects


Melia azedarach




many insects




Stops many insects feeding on plants



Ground peppercorns


Ants, cats, possums




Spray or dust


Aphis, slugs, snails





Mildew and damping off on seedlings



Wood chips


Aphis, sawflies, Caterpillars


In the UK:

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