Trends in the Evolution of Pesticides

1. A decrease in the persistence of the chemicals in the environment (increase in water solubility as opposed to fat solubility).
2. The introduction of insecticides that are more selective (i.e. are less harmful to non-target organisms, including humans).
3. A movement toward lower application rates of product/area. This includes developments in application technology such as ultra-low volume (ULV) sprayers, which employ "spinning disc" and "electrostatic" technologies.
4. The development and use of pest "thresholds". The pesticide is only applied once the pest has reached a particular predetermined level (instead of simply applying the pesticide as an insurance whether it is needed or not.)

This "evolution" has been partly responsible for a steady decline in the application of insecticides in some developed countries. For example, in the United States there has been a 51% reduction in the application of insecticides during the period from 1979 to 1991 (Larson, 1996)

But reduced quantity does not necessarily mean less toxicity as newer generation pesticides are much more potent even as less is required for effective application.

Also, greater selectivity can lead to unintended problems as opportunistic insects, for example, fill the void left by the intended target insect and become pests themselves.

Finally, as pesticides have become more chemically complex, their research and development costs have also risen; the growth of environmentalism and the increased stringency of safety standards have also added costs to development, which are passed on to the farmer, consumer and taxpayer.

(Integrated Pest Management-Ideals and Realities in Developing Countries, 1997)