Insecticidal activity of the avermectins
James, P.S.; Picton, J.; Riek, R.F.
Veterinary Record 106(3): 59
1980
ISSN/ISBN: 0042-4900 PMID: 7361432 Document Number: 160405
Avermectins have been found to possess activity against a wide range of nematodes, insects and other arthropods, a number of which are important in the fields of agriculture and animal and human health [see also RAE/B 68, 18]. Their activity was tested in the laboratory in Australia against Lucilia cuprina (Wied.), and a crude extract was found to be highly active against larvae of a strain susceptible to organophosphates, the LC50 being approximately 0.12 p.p.m. When purified extracts were tested, fractions A1a and A2a showed LC50s of about 0.0058 and 0.0175 p.p.m., respectively (as did B1a and B2a avermectins), as compared with about 0.03 p.p.m. for diazinon. In a pen-trial with sheep, patches of wool were saturated with a crude mixture of avermectins and challenged weekly with artificial implants of L. cuprina larvae. The treatment afforded protection for up to 31 weeks as compared with 10 weeks for diazinon at a comparable concentration. In a further larval-implant trial with sheep subjected to outdoor conditions, a mixture of 'A' avermectins gave up to 13 weeks' protection against susceptible larvae and 12 weeks' protection against organophosphorus-resistant larvae. Diazinon under the same conditions and at a comparable concentration gave 10 weeks' and 4 weeks' protection, respectively.