Muscarinic agonists provide a new class of acaricide

THE resistance of ticks to chemical methods of control is an increasingly serious problem 1–5 , and new classes of compounds with high acaricidal activity and low mammalian toxicity are needed urgently. In the search for novel acaricides the nervous system is a prime target, and, in spite of evidence about the role of γ -aminobutyrate and gluta-mate in arthropod nervous transmission, acetylcholine is the only well established neurotransmitter 6–9 . So far only acetylcholinesterases have achieved an important role in the disruption of cholinergic neurotransmission. Anti-cholinergics, such as atropine, are ineffective, and cholino-mimetics other than nicotine have been little investigated. We now report that certain muscarinic agonists are potent acaricides.