Overuse of chemicals to control pests

Indiscriminate use of pesticides
Use of inappropriate rodenticides
Use of illegal fungicides
Excessive use of weedicides
Misuse of insecticides aggravates resistance
Abuse of biocides against pests
The problems of controlling insects and other pests have reached an all-time high. Pest control researchers, extension specialists and farmers are faced with mounting pest problems while certain avenues to solutions are meeting constraints of a technical, economic or social nature. These problems include: the damaging effects of persistent pesticide residues on terrestrial fresh water and marine organisms; the destruction of beneficial controlling organisms, thereby causing an increase in the number of pest species and their abundance; and the development of pest strains resistant to the pesticides used to control them. This resistance has in turn led to use of a still greater variety of pesticides and their use in greater quantities. In some situations it has become uneconomic even to attempt to control certain crop pests, and large areas have suffered great economic and social stress.
The global use of agricultural pesticides rose from about 50 million kilograms a year in 1945 to current application rates of approximately 2.5 billion kilograms per year. Most modern pesticides are more than 10 times as toxic to living organisms than those used in the 1950s.

Cotton bollworms were not a big problems until farmers decided to spray them. Most of the bollworms were controlled by natural predators. With the use of pesticides the predators were killed.

Accumulation of pesticides in soils and waters may eventually render crops unsuitable for consumption. Excessive application of pesticides is a sign of bad agricultural practice, and a contributory factor in the problem; but non-observance of the necessary waiting time between last application and harvest is the main cause of increased residues.
The use of pesticides has helped to reduce crop losses due to all kinds of pest organisms. Crop losses due to pests are so severe in some places that there are good arguments for increasing pesticide application. At the same time, the demand for increased testing of new pesticides for environmental effects is slowing their introduction by industry, and meanwhile, pests in ever-increasing numbers are developing resistance to the older types. A sample of 38 developing countries applied 162,000 tonnes of pesticides in 1973, and this represented a 23% increase over the preceding few years. But to reduce serious pest damage, pesticide use should have been five times greater in the developing countries by 1985 than it was in 1970/71.
(D) Detailed problems