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An insecticide is a substance used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to be a major factor behind the increase in agricultural 20th century's productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans; some concentrate along the food chain. Insecticides can be classified in two major groups as systemic insecticide which have residual or long term activity and contact insecticides, which have no residual activity. Furthermore, one can distinguish natural insecticides, such as nicotine, pyrethrum and neem extracts, made by plants as defenses against insects, inorganic insecticides, which are metals, versus organic insecticides, which are organic chemical compounds mostly working by contact. The mode of action describes how the pesticide kills or inactivates a pest. It provides another way of classifying insecticides. Mode of action is important in understanding whether an insecticide will be toxic to unrelated species, such as fish, birds and mammals. For products that repel rather than kill insects see insect repellents. ==Type of activity== Systemic insecticides become incorporated and distributed systemically throughout the whole plant. When insects feed on the plant, they ingest the insecticide. Systemic insecticides produced by transgenic plants are called plant-incorporated protectants (PIPs). For instance, a gene that codes for a specific Bacillus thuringiensis biocidal protein was introduced into corn and other species. The plant manufactures the protein, which kills the insect when consumed.〔(Plant Incorporated Protectants )〕 Systemic insecticides have activity pertaining to their residue which is called "residual activity" or long-term activity. Contact insecticides are toxic to insects upon direct contact. These can be inorganic insecticides, which are metals and include arsenates, copper and fluorine compounds, which are less commonly used, and the commonly used sulfur. Contact insecticides can be organic insecticides, i.e. organic chemical compounds, synthetically produced, and comprising the largest numbers of pesticides used today. Or they can be natural compounds like pyrethrum, neem oil etc. Contact insecticides usually have no residual activity. Efficacy can be related to the quality of pesticide application, with small droplets, such as aerosols often improving performance. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Insecticide」の詳細全文を読む スポンサード リンク
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