The chemical class chloronicotinyl is a relatively new one that contains a number of systemic insecticides that are registered for use in greenhouses. These include imidacloprid (Marathon), acetamiprid (Tristar), and thiamethoxam (Flagship). These materials are transported throughout the plant in the transpiration stream and provide a certain degree of residual activity after application. The products currently available vary in their water solubility, which affects how rapidly the active ingredient is taken up by the plant.
Chloronicotinyls have a different mode of action, compared to organophosphates (Orthene and Duraguard), carbamates (Mesurol), pyrethroids (Talstar, Decathlon, and Mavrik), and macrocyclic lactone (Avid). Chloronicotinyl insecticides kill target pests in a similar manner as the natural product nicotine, by acting on the central nervous system, causing irreversible blockage of the postsynaptic nicotinergic acetylcholine receptors. These insecticides disrupt nerve transmission in insects, causing uncontrolled firing of nerves. This results in rapid pulses from the steady influx of sodium, leading to hyperexcitation, convulsions, paralysis, and death. A general characteristic of chloronicotinyl insecticides is that they are highly effective in controlling phloem-feeding or sucking insects, including aphids, whiteflies, and mealybugs; however, they are not active on spider mites (that is, twospotted spider mite).
Because all three commercially available chloronicotinyls have similar modes of activity, it is important not to rotate from one chloronicotinyl to the next, as this would increase the selection pressure on the target pest population and may potentially enhance the development of resistance. To avoid the issue of resistance, use an insecticide with a different mode of activity either before or after using a chloronicotinyl insecticide.