For instance, a gene that codes for a specific Bacillus thuringiensis biocidal protein was introduced into corn ( maize) and other species. Systemic insecticides produced by transgenic plants are called plant-incorporated protectants (PIPs). When insects feed on the plant, they ingest the insecticide. Systemic insecticides become incorporated and distributed systemically throughout the whole plant. Insecticides are distinct from non-insecticidal repellents, which repel but do not kill. This is slower than some other methods, but usually completely eradicates the ant colony. Over time, this eliminates all of the ants including the queen. As they return to the nest they take insecticide with them and transfer it to their nestmates. Social insects such as ants cannot detect non-repellents and readily crawl through them. Insecticides may be repellent or non-repellent. Mode of action can be important in understanding whether an insecticide will be toxic to unrelated species, such as fish, birds and mammals. It provides another way of classifying insecticides. The mode of action describes how the pesticide kills or inactivates a pest. Insecticides can be classified into two major groups: systemic insecticides, which have residual or long term activity and contact insecticides, which have no residual activity. Nearly all insecticides have the potential to significantly alter ecosystems many are toxic to humans and/or animals some become concentrated as they spread along the food chain. Insecticides are claimed to be a major factor behind the increase in the 20th-century's agricultural productivity. Insecticides are used in agriculture, medicine, industry and by consumers. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are substances used to kill insects. Farmer spraying an insecticide on a cashewnut tree in Tanzania
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