Organic Chemicals

Organic gardeners do not like to use chemicals in their gardens, preferring instead to use methods such as companion planting to deter pests. There are occasions though when they have to resort to chemicals

There are several fungicides and pesticides available that are classed as 'organic' as they don't remain active for very long, a day or so at the most.

Below is a list of the various chemicals and their uses.

Chemical Use

Bordeaux Mixture

This is a mixture of copper Sulphate and slaked lime. It is used to control Blight and Mildew.

Burgundy Mixture

Mixture of coppers Sulphate and washing soda. Used to control Mildews.


Used as a pesticide for controlling caterpillars etc. It is not selective so should only be used as a last resort. It is also harmful to fish.
Insecticidal Soap Potassium - salt. Used as a pesticide in the control of Aphids, Whitefly, Red Spider Mites, Scale insects and Mealy Bugs. Only works on direct contact with the insect and persists for one day. Slightly more effective than Soft Soap.
Soft Soap Traditional control for Aphids and Red Spider Mites. Only works on direct contact with the insect and persists for one day. Can be used as a 'wetting agent' in conjunction with other sprays.
Nicotine Because it is non-persistent, it is allowed as a pesticide by organic bodies. It is however, highly poisonous and can be fatal if taken in it's concentrated form. Best avoided.
Quassia Though harmless to Ladybirds and Bees, it is very effective against Aphids, some caterpillars, leaf miners and sawfly.


Derived from the Pyrethrum plant, is used as a pesticide which is effective against most insects, especially Aphids. However, it is not selective and can harm beneficial insects as well. Harmless to animals.
Dispersible Sulphur Organic bodies are in dispute if whether this is organic or not. Used as a fungicide against fungi and rust.

Using Pesticides and Fungicides

It is well to remember that even when using these 'Safe' chemicals, it is wise to treat them as you would if they were dangerous.

Remember: -

  • Do not put chemicals where children or pets can reach them
  • Always leave the chemicals in their original containers. This ensures that you know what they are how to use them.
  • Always use as directed on the packaging.
  • Avoid spraying beneficial insects. Most of these chemicals will kill beneficial insects as well as pests.
  • Wash equipment thoroughly after use and never keep left over solutions. Dispose of them safely.
  • Spray only on windless days; preferably in the evening after beneficial insects have 'gone to bed'.
  • Never spray any open flowers, as this is when bees visit and can be harmed.

© copyright 1999, P. A. Owen

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