Afidopyropen (ME-5343) is a new and promising insecticide with an unknown mechanism of action that is effective against sucking insects. Afidopyropen was highly toxic to pea aphids (Acyrthosiphon pisum), being more toxic than six other widely used insecticides. In contrast, it was practically non-toxic to eight other species of insects we tested. Afidopyropen was not toxic to American cockroaches via injection, suggesting that lack of toxicity in this species is not due to lack of cuticular penetration. House flies are insensitive to afidopyropen by topical, residual and feeding exposure. Addition of synergists did not change this result, suggesting that insensitivity to afidopyropen in house flies is not due to rapid detoxification nor is it dependent on the method of bioassay used. Afidopyropen did not cause firefly lanterns to glow, nor did it prevent the octopamine stimulated lantern glow. Extracellular recordings of action potentials from a tonically active motor nerve of crayfish in situ showed no effects of afidopyropen at concentrations up to 10-5M. These results suggest that the target site of afidopyropen is not the voltage gated sodium channel, voltage gated potassium channel, GABA gated chloride channel, nicotinic acetylcholine receptor, acetylcholinesterase, octopamine receptor or glutamate receptor. Afidopyropen injected in to crayfish caused flextion of the legs and tail, similar to the symptoms induced by 5-HT (serotonin). We evaluated the effect of afidopyropen on 5-HT2-like receptors with intracellular recordings of excitatory post-synaptic potentials from the peripheral neuromuscular junction of the crayfish and found no effect of afidopyropen. Thus, afidopyropen was neither an agonist nor antagonist of 5-HT2 receptors, did not affect neurotransmitter release and did not affect glutamate receptors. We conclude that afidopyropen is highly toxic to aphids and that this is due to a unique, and currently undefined mechanism of action.

Afidopyropen is highly toxic to aphids via a unique mechanism of action

248th National Meeting (2014)

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