Classification of pesticides

Knowledge about a certain pesticide often starts by learning how it is classified. Pesticides can be classified or grouped in many different ways. Try answering the following questions:

Which pests does it control?

  • Insecticides (insects)
  • Fungicides (fungi)
  • Bactericides (bacteria)
  • Herbicides (weeds)
  • Acaricides, miticides (mites)
  • Rodenticides (rodents)

What is the source?

  • Synthetic pesticides (chemicals manufactured by humans, they do not occur in nature)
  • Organic pesticides (produced from animal or plant parts)

Preparing bio-extracts
“Many different ingredients are used to prepare a bio-extract that will be used as an organic pesticide.

What is the mode of action?

  • Stomach poisons (they have to be eaten)
  • Contact poisons (they work via the skin)
  • Fumigants (they produce a vapor that kills organisms)

What do you know about the target range?

  • Broad spectrum pesticides (chemicals that kill a wide range of pests)
  • Selective pesticides (chemicals that kill only a specific pest or group of pests)

What is the active ingredient?

Synthetic pesticides can be grouped by their active ingredient (the chemical class to which a toxic components belong. Major chemical groups are:

  • Carbamates
  • Organochlorines
  • Organophosphates
  • Pyrethroids
  • Thiocarbamates
  • etc.

Each of these chemical families is know to cause certain general health effects.

Most pesticide products will have only one active ingredient, but sometimes they will have more than one active ingredient.

Does it move in the plant?

  • Systemic pesticides (these products are taken up by the plant, for example through the roots or the leaves, and move through the plant to other untreated parts of the plant)
  • Non-systemic pesticides

How is it formulated?

  • Liquids
  • Powders
  • Granules
  • Baits
  • Dusts
  • Smoke generators
  • Ultra low volume (ulv) liquids
  • etc.

To what toxicity class does it belong?

Skull warning red background

Another way of grouping pesticides is according to the potential risk to human health. The World Health Organization (WHO) has developed the following toxicity classes for chemical pesticides:

  • Class Ia = Extremely hazardous
  • Class Ib = Highly hazardous
  • Class II = Moderately hazardous
  • Class III = Slightly hazardous
  • Class IV = Product unlikely to present acute hazard in normal use

Are you allowed to use it?

  • Registered pesticides
  • Banned pesticides

By law you are only allowed to use registered products. Presently, in Thailand about 310 different active ingredients are registered. About 80 active ingredients that were registered in the past have now been banned and can not be used any more.

More questions?

Yes, besides the above questions that help to classify pesticides, there are many more questions to be answered. For example:

  • What does it do to non-target organisms, such as bees, birds, fish, etc.?
  • What does it do to natural enemies (spiders, parasitoids, predators, antagonistic fungi, etc.)?
  • How much does it cost?
  • Does it break down rapidly or is it a persistent chemical?
  • What to do in case of accidental poisoning?
  • etc.

Never use a pesticide before you have answers to all the relevant questions and always ask yourself if there is a safer alternative!

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