PHYTOCHEMICALS: can sprays be safe?

Since the discovery of chemical compounds which can be employed in agriculture, spraying, fumigating and dusting have been the most widely used methods in pest and disease control. The development of more and more effective phytochemicals and their increasingly widespread use are causing concern among biologists and environmentalists because they state that man is altering nature's balance and endangering health and the food supply. 

Organic agriculture does not use artificial fertilizers or pesticides as they are compounds with high biological activity, which tend to have harmful consequences on physiological processes. Moreover, they may stimulate the growth of new pathogens and pests as they kill antagonistic organisms. However, sometimes chemicals must be used in organic production when there is a persistent and recurrent problem, which cannot be solved with completely organic products; so they can be used along with biological control techniques, when proved that they do not harm the rest of the system. 

Whatever their nature is, all sprays must be applied to crops correctly. This is essential both to ensure that they are effective and to minimize the harm to the environment. 

(Thanks to Lorenzo S. for helping me writing this post)