It’s important we know how insecticides work. If we don’t know how insecticides work we may be contributing to global insecticide resistance.
Insecticides are a subclass of pesticides aimed to kill insects. Pesticides is a class of chemicals that also kill other species classed as pests such as rats and mice and plants such as weeds.
All insecticides have at least one active ingredient. Typically, the active ingredient(s) is listed on the front of the label. For example, most of us know the active ingredient in Round Up is glyphosate. That’s a herbicide – it kills plants, generally.
The active ingredient in a pesticide has a particular mode of action. It works in a particular way that is targeted in the organism. Some insecticidal modes of action include suffocation and this is a respiratory target site. Generally, these are commonly called contact insecticides but contact insecticides have various modes of action.
Contact insecticides only need to have contact with an insect to harm them.
Some insecticides attack the central nervous system and/or the connections between neurons. That is the nerve or muscular target site. They can be contact or systemic in nature.
Systemic insecticides need to be taken in to be effective. Typically, a plant absorbs the active ingredient and when an insect feeds on the plant (leaves, stem, sap, pollen, nectar) they get poisoned.
So how they work, their mode of action refers to how the chemical affects the physiological target of the insect. It’s important to understand that all insecticides – natural and synthetic have modes of actions. They all have ways of killing insects. That is the key effect of insecticides.
Five modes of action
Insecticides work by targeting a particular part of the body. There are five main target sites (modes of action) for insecticides:
Nerve and muscle targeting insecticides. These are usually fast acting;
Growth is inhibited by the application of hormones and other growth inhibitors that promote an insect to remain a juvenile. These insecticides are typically very slow acting;
Respiration is affected and these insecticides are moderately fast acting;
Midgut based insecticides are based on microbial interactions; and
Unknown or non-specific insecticides and target sites.
The effect of insecticides are much more complex and diverse. When we use them, we think we are affecting just the insects we’re targeting. However, after reading my blog on the Effect of Insecticides, we may think differently.
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