Greenhouse Pesticides
Chemical Pesticides
Conventional pesticides (i.e., synthesized by the agrochemical companies) are man-made and are the largest group of pesticides used by growers. There are many classes of synthetic pesticides. The main classes consist of organochlorines, organophosphates, carbamates, and pyrethroids. The synthetic compounds include most of the insecticides, herbicides, and fungicides. If all other integrated pest management tactics are unable to control pest populations, then use of a pesticide to control the pest and prevent economic loss is justified. In most cropping systems, pesticides are still the principal means of controlling pests. They can be relatively cheap and are easy to apply, fast-acting, and in most cases, can be relied on to control the pest(s).
Types of Chemical Pesticides
The main classes consist of organochlorines, organophosphates, carbamates, and pyrethroids. There are also chemical subclasses of pesticides, but these are beyond the scope of this discussion. Pesticides with similar structures have similar characteristics and usually have a similar mode of action. Before using any pesticide, it is important to understand its relative toxicity, mode of action, rate of application, mixing and application guidelines, reentry intervals, persistence, and environmental impact. One can learn most or all these issues by reading the most current label.
Organochlorines (Chlorinated Hydrocarbons)
Controls pests by disrupting nerve-impulse transmission (disrupts ion flow at the axon/synapse level). Generally persistent in soil, food, and in h
Organophosphates
The chemical structure of organochlorines is diverse, but they all contain chlorine, which places them in a larger class of compounds called chlorinated hydrocarbons. Organophosphates were developed to replace some of the chlorinated hydrocarbons. Organophosphates break down more rapidly in the environment and are less likely to pose an environmental risk.
Carbamates and Thiocarbamates
Carbamates are broad-spectrum pesticides that are effective against a variety of pests. Carbamates are considered slightly less toxic than organophosphates because they are rapidly processed by the body (metabolized) and excreted. Carbamates also do not persist in the environment for as long as organophosphates, and usually breakdown within days to weeks.
Pyrethroids (synthetic)
Synthetic pyrethroids are synthetic versions of the naturally occurring pyrethrins. Pyrethroids exhibit greater stability in the environment, and are therefore more persistent. They are also designed to target specific pest species. The mode of action of pyrethroids is identical to that of pyrethrins.
Diamides
Diamide insecticides have emerged as one of the most promising new classes of insecticide chemistry owing to their excellent insecticidal efficacy and high margins of mammalian safety.
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