Pesticides are substances applied to plants to control pests, including insects, fungi, weeds, and rodents. These chemicals function by disrupting specific biological processes within target organisms, such as the nervous system of insects or the cellular metabolism of fungi. They are formulated based on various chemical compounds and biological agents, and their effectiveness relies on maintaining sufficient concentrations at the application site. Due to their mode of action, the use of pesticides requires careful consideration of potential environmental persistence, non-target organism toxicity, and the necessity of integrated management practices to ensure safe and sustainable agricultural output.