Pesticides are incredibly important to industrial-scale, input heavy agriculture, although they are also used in the small scale on home horticulture and agriculture projects. They are usually sprayed by handheld dispensers or from overhead, by low-flying aircraft or automated irrigation systems. There is considerable debate as to whether the benefits of pesticides outweigh the drawbacks in the long term.
Time and Labor Saving
Pest control on crops is of paramount importance in bringing a healthy, attractive, consistent and desirable product to market. Insects, parasites, vermin, bacteria and other organisms can directly harm crops, lowering yields and spreading disease. Controlling these pests on a plant by plant basis by hand is extremely time consuming, whereas mass spraying of crops is quick, and, theoretically, requires minimal effect.
Typically, vegetables and fruits are washed thoroughly before being prepared for shipping, but occasionally, traces of harmful chemicals can be left behind on produce. One extremely notable example of pesticide contamination is in agricultural runoff water, which can contain insoluble compounds that pollute streams, reservoirs and rivers.
The time saved by not managing the myriad pests that can ruin crops by hand is practically immeasurable. This type of efficiency and intensive use of inputs literally makes modern agriculture possible and has contributed to the largest and most consistent food surpluses in human history.
Wiping out local populations of pests can have an effect on the predators of those pests, which may lead to partial or total habitat collapse. Long-acting pesticides may work their way into the diets of animals throughout the ecosystem as well, creating a similar effect. The entire DDT controversy was based on the fact that this anti-mosquito drug severely affected some birds of prey, which was an unintended consequence.