Pesticides Part 1: An introduction to pesticide pollution

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With the FAO estimating that annually between 20 to 40 percent of global crop production are lost to pests, it is no surprise that pesticides have become a mainstay of modern farming, with approximately 5.6 billion pounds used worldwide. The use of pesticides reduces the effect of pest attacks diseases and weeds, thus contributing to higher yields overall.

Figure 1: Pesticides prevent or mitigate crop losses from pest attacks.

But what are pesticides exactly? At their core, they are substances that act as biocides with ability to kill one or more organisms, generally pests, diseases and weeds that are noxious or unwanted in agricultural settings. They come in various liquid or solid formulations: Liquid formulations indclude aqueous, emulsifiable or suspended concentrates. While solid forms may come in the form of powder or granules that can either be directly applied or dissolved in a solvent, typically water.

Due to the great variability in the active ingredients of pesticides, their mode-of-action is often just as variable and complex, but typically causes a toxic effect by disrupting physiological or biochemical processes of the pest or ‘target’ organism. The most common modes of action are (Hassall, 1990):

  • Poison Ingested by the pest organism before releasing toxins into its stomach.
  • Contact Applied directly to the pest organism, penetrating its surface and producing a localised toxic effect. Usually they remain active for a few days at most.
  • Residual Act in the same way as contact pesticides, but do not need to be applied directly to the pest organism since they remain active for long periods.
  • Translocated Active ingredient is mobilised within the pest organism and has a more effective toxic effect upon it.
  • Systemic Active ingredient is mobilised within the crop or animal being protected and is then transferred to the target pest

These effects of these may either be acute (rapid or immediate onset; imagine spraying bugs with bug spray at home) or chronic (onset and persistence of effects may occur over a long time period), and are dependent on the type and dosage of the pesticide.

In the following posts we will be covering the types of pesticides how they work and the kinds the problem they cause in the environment!

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