The development of crop protection chemicals

As we have seen, there were no effective fungicides until 1882, apart from the dusting of powdery mildews with flowers of sulphur. And, until 1940, and the discovery of DDT, there were no effective insecticides, and farmers were using some very dangerous poisons, such as compounds of lead, arsenic, mercury, and cyanide to control Colorado beetle of potatoes, codling moth of apples, and other major pests.

The discovery of the fungicide Bordeaux mixture, by Millardet, in 1882, initiated the age of crop protection chemicals. A surge of developments in both chemistry and application methods followed. As a consequence, there was a steady decline in the use of host plant resistance, and a steadily increasing reliance on crop protection chemicals. This situation was aggravated by the tendency to screen breeding populations of plants under the protection of either vertical resistance or of crop protection chemicals. These techniques led to a serious decline in the levels of horizontal resistance (see 5.3.4).

One of the more tragic aspects of this reliance on crop protection chemicals was their instability (see 10.6) resulting from the appearance of new strains of the crop parasites that were resistant to the chemical in question. This was a situation little different from the 'boom and bust' cycle of vertical resistance breeding.

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