a1 Ministry of Agriculture, Fisheries and Food, Harpenden Laboratory, Hatching Green, Harpenden, Herts AL5 2BD, UK
Baseline responses of United Kingdom field populations of Macrosiphum euphorbiae (Thomas) and Brevicoryne brassicae (L.) to demeton-S-methyl were investigated using the FAO-recommended dip-test bioassay. Dose-response lines were produced, and discriminating doses for the two species were derived from the results (320 and 500 mg a.i./litre, respectively) and validated by testing further field populations at those single doses. Of the 1620 individuals of M. euphorbiae and 330 of B. brassicae tested, none survived the discriminating doses.
(Received May 31 1984)