Then the cycle begins again, resulting in increased costs, increased amount of chemical use and ever decreasing effectiveness of products . Isley also studied the biology and ecology of the boll weevil and used this information in a pest management system. This effect can be useful for controlling several pests at once. Often however, insects that were not a problem in the cropping system then suddenly become pests. This is because most insect species are kept under control naturally by other parasitic or predaceous insects, mites or spiders.
Pesticides affect other parts of the ecosystem as well.
Pesticide use has lead to groundwater contamination, fish and bird kills, accumulation of certain compounds in the food chain, poisoning of individuals working with the chemicals improperly and even from ingesting food contaminated with chemicals improperly used or applied. As a result of the problems associated with pesticides, the late 1960s and early 1970s saw increased environmental activism, education and regulation of most aspects of pesticide registration and use at both the state and federal levels.