What are the characteristics of organophosphate insecticides?
Organophosphate insecticides are the most widely used and highest-volume class of insecticides in China. They come in many varieties with widely differing properties, but taken together they have the following characteristics: (1) A relatively broad insecticidal spectrum. The organophosphate insecticides commonly used today can control many agricultural and forestry pests, and some can be used to control public health pests...
Organophosphate insecticides are the most widely used and highest-volume class of insecticides in China. They come in many varieties with widely differing properties, but taken together they have the following characteristics:
(1) A relatively broad insecticidal spectrum. The organophosphate insecticides commonly used today can control many agricultural and forestry pests, and some can be used to control public health pests and external parasites of livestock and poultry.
(2) Diversified modes of action that meet a wide range of needs. Most varieties have contact and stomach poison action, some have systemic or penetrating action, and a few have fumigant action, so they can be applied in various ways to control above-ground, soil-dwelling, boring and piercing-sucking types of agricultural and forestry pests. Their insecticidal mechanism is to inhibit the activity of cholinesterase in the pest's body, disrupting normal nerve transmission and causing a series of nervous system poisoning symptoms until death.
(3) Relatively high toxicity, so safety precautions should be taken when using them. Most varieties are fairly toxic to humans and livestock, and some are highly toxic, such as phorate, methamidophos and demeton. Safety precautions should be taken during use, and a certain pre-harvest interval must be observed to avoid poisoning from pesticide residues.
(4) They degrade easily in the environment. Most varieties readily break down into non-toxic substances in plants and animals, and under natural conditions such as sunlight, wind and rain they readily hydrolyze and oxidize. Therefore, they should be stored away from light and moisture.
(5) Easy detoxification. Although organophosphate insecticides are relatively toxic and can easily cause poisoning in humans and livestock, highly effective antidotes such as atropine and pralidoxime are widely available.
(6) Resistance develops relatively slowly, and they are relatively safe for crops. Although organophosphate insecticides have been used for a very long time and their efficacy has declined somewhat compared with the beginning, pest resistance to them has developed relatively slowly, and they are still used in large quantities today. At the same time, they are generally relatively safe for crops and unlikely to cause phytotoxicity, though certain crops are sensitive to particular varieties, such as trichlorfon causing phytotoxicity to sorghum, and dichlorvos and omethoate causing some phytotoxicity to corn and peach trees at high concentrations.
(7) The vast majority of organophosphate insecticides decompose easily under alkaline conditions, so they must not be mixed with alkaline substances.
At present, the organophosphate insecticide varieties registered and widely used in China mainly include: parathion, methyl parathion, methamidophos, acephate, isocarbophos, dimethoate, omethoate, dichlorvos, malathion, phoxim, monocrotophos, phorate, chlorpyrifos, triazophos, isofenphos-methyl, trichlorfon, methidathion, profenofos and so on.