An insecticide made of organophosphates is acephate. It is applied as a seed treatment to citrus trees, food crops, golf courses, and commercial or institutional buildings. Acephate was once widely utilized in and around homes, but the majority of those uses are now prohibited. The U.S. EPA has been registering acephate since 1973.
What is Acephate?
Acephate is a contact and systemic organophosphate insecticide that was approved for use in the United States in 1973. It is used to control insects on food crops such as beans, lettuce, and bell peppers as well as in residential and commercial buildings, food handling facilities, ornamental plants, sod, and turf.
Acephate has a low affinity for soils, is nonvolatile, highly water-soluble, and has a moderate potential for runoff into surface waterways. In the environment, acephate degrades quickly to produce methamidophos, a much more deadly organophosphate pesticide. Acephate toxicity in insects is mostly caused by its conversion to methamidophos since insects also undergo a similar change. Acephate does not bioaccumulate but is immediately harmful to honey bees after application (U.S. EPA, 2006).
Acephate Uses
- Acephate is a general-purpose insecticide that has been approved for use on horticultural nursery plants, food crops, agricultural seeds, non-bearing plants, institutions, and commercial structures, such as public health facilities.
- Caution to danger is a possible signal phrase for products that contain acephate. The warning phrase is the product’s overall toxicity when the active ingredient and other chemicals are combined together.
Mode of Action:
Target Organisms
- Acephate is a systemic insecticide that can be applied directly to the skin or consumed to get rid of biting and sucking insects.
- Acephate is an example of an organophosphate that binds to and inhibits the acetylcholinesterase (AChE) enzyme in nervous system tissues. In response to this, acetylcholine, a neurotransmitter, builds up and frequently activates cholinergic receptors. Acephate is a minimal acetylcholinesterase inhibitor on its own. Acephate is not as powerful an organophosphate as methamidophos. Acephate is metabolized more quickly by mammals into des-O-methylacephate than by insects, which explains why acephate has relatively high selectivity against insects. Insects convert acephate to methamidophos by hydrolysis.
- Through phosphorylation, methamidophos prevent acetylcholinesterase from working. Acetylcholinesterase degrades acetylcholine, which is a common insect stimulatory neurotransmitter for motor, sensory, and intermediate neurons. Acetylcholine levels rise as a result of organophosphates, which overexcite the target neurons, muscles, or tissues.
Non-target Organisms
- Compared to insects, mammals are less vulnerable to acephate. Acephate’s efficacy or selectivity is dependent on mammalian metabolism. The major pathway of acephate’s conversion into des-O-methylacephate, also known as S-methylacetyl phosphoramidothiolate (SMPT), which is not a cholinesterase inhibitor, is where most of the mammalian metabolism of acephate into the cholinesterase inhibitor methamidophos occurs.
- In mammals, cholinesterase is inhibited by organophosphates such as acephate and methamidophos. Acephate is a marginal cholinesterase inhibitor, though. In comparison to acephate, methamidophos is more poisonous to both invertebrates and vertebrates.
- Cholinesterase in mammals is inhibited by organophosphates such as acephate and methamidophos. A mild cholinesterase inhibitor, however, is acephate. Compared to acephate, methamidophos is more harmful to both invertebrates and vertebrates.
- According to other researchers and authors, acephate prevents methamidophos from binding to acetylcholine in mammals either directly or via an allosteric site. See the metabolism section.
- Methamidophos inhibited erythrocyte and brain acetylcholinesterase in rat experiments in vitro thousand times more efficiently than acephate. Methamidophos is ten times more effective than acephate at suppressing cholinesterase in mice, according to another study.
- One study on white-throated sparrows found that acephate consumption inhibited brain cholinesterase. Acephate was administered to hens in a study that revealed it inhibited acetylcholinesterase and, to a much lesser level, neuropathy target esterase.
- Although acephate is typically thought to be non-phytotoxic, it has been seen to cause leaf burn on Red Delicious apples after application.
Summing Up
Acephate is a systemic insecticide that successfully eradicates a wide range of pests on ornamental plants, cotton, beans, head lettuce, and animal parasites. As it is less hazardous than methamidophos, it makes a good replacement. Methamidophos is a class IV “very toxic” pesticide, whereas acephate is a class II “moderately hazardous” insecticide (World Health Organization [WHO], 2009). Acephate is very water-soluble, rapidly absorbed by plants, and builds up in edible plant sections. It can easily pollute soil and groundwater.
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