In her book “Living Downstream” American ecologist Sandra Steingraber records that less than 20 insect species showed pesticide resistance in 1950; in 1960 there were 137 species that were resistant to at least one pesticide, and in 1990 there were 504 pesticide resistant insect and mite species.
In the 1950s herbicide resistant species were unknown; there are now around 300 plant species that show herbicide resistance.
Steingraber also reports that in the 1940s, when crop rotation and other organic farming techniques were practiced only seven percent of crops were damaged by insects – in the 1980s despite the addition of chemical pesticides 13 percent of crops showed insect damage, but this has been offset by higher yields.
With reference to American crops, maize is one of the largest users of insectides, with a 1,000 fold increase in the use of use of pesticides since 1945. The United States Department of Agriculture reported.