Chemical treatment of House Plants

It is well worth having an idea of the types of chemical treatment available and the ways they work. Different pesticides attack different pests, and some are harmful to pets and fish, so acquiring a working knowledge of the names of the chief ingredients in chemical sprays and powders will help you choose a preparation that is just right. The active ingredients involved in ‘chemical warfare’ can be divided into pesticides, fungicides and herbicides.


Pesticides, or insecticides as they are also called, are used to kill the insect pests which damage plants by eating the leaves, stems or roots or by sucking the sap. They are poisons that attack the insects, either on contact or when eaten by the pests.Chemical treatment of House Plants

The so-called contact pesticides (those that attack the pests directly) must hit their target and need to be sprayed or dusted directly onto the insects, while the second type of poison must completely cover the parts of the plants which the pests attack, to make sure that they will ingest it.

Systemic pesticides are a fairly modern type of treatment in which the poisons are absorbed by the plant and carried round in the sap to every part of the plant. As a result, wherever the pests attack, they have no escape. Systemic poisons are more sure in their effect, but take a little longer to act.

Systemic pesticides are particularly useful where there is a bad infestation or when pests attack inaccessible parts, such as the undersides of crinkly leaves.


Fungicides can be used to cure plant diseases caused by fungus attacks, for example the various types of rot and mould that can deface and eventually kill , house plants. Like insecticides, these

‘treatments are in some cases available as systemic chemicals which work from within, while other forms of treatment are effective only where they are applied. Systemic control is especially helpful when the plant is badly affected and when parts of the plants are inaccessible.


Herbicides are chemical weed killers, and may be useful on the balcony or patio. They are available in contact and systemic versions, and it is the second kind that come into their own when virulent weeds are tangled up in the dense growth of a healthy outdoor plant. Systemic weedkillers can be painted onto any part of the offending weeds, and will be carried through the whole plant. The herbicides sold for broad-leaved lawn weeds are suitable for this use. They must be applied with great care to avoid other plants.

Safety Checklist

  • All chemicals are potentially harmful, and should be used with care.
  • Check from the pack label that the product is suitable for the plant. For example the insecticide HCH kills most insects, but harm some plants.
  • Read the advice on the label before using, as chemicals can be harmful to pets. For example, the insecticide Rotenone, the main ingredient of Derris is relatively safe to use, although it will kill fish.
  • Use according to the manufacturer’s instructions. Too strong a dose can kill, as can holding an aerosol too close to the plant.
  • Avoid breathing in chemicals, and wash hands thoroughly after use.
  • Never transfer chemicals to other containers. Always keep chemicals in their own containers and make sure that the instructions are legible. Labels rub off, so keep a note of how to use.
  • Always use the recommended dose.
  • Never use near fish tanks or when pets are around.
  • When resorting to pesticides try to use the safest — those which do not attack the useful insects needed for successful plant pollination and which prey on other pest insect species.

Keeping plants healthy

Healthy house plants are much less likely to suffer from pests and diseases.

So getting to know your plants and developing an understanding of their likes and dislikes is the key to avoiding problems.

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