RESISTANCE TO 2 ORGANOPHOSPHORUS INSECTICIDES IN NEW-ZEALAND POPULATIONS OF THE AUSTRALIAN SHEEP BLOWFLY, LUCILIA-CUPRINA

A treated-surface test was used in a bioassay to detect insecticide re sistance to the organophosphorus compounds diazinon and propetamphos, in larvae of field strains of Lucilia cuprina in New Zealand during 19 90/91 and 1991/92 (December-April). Mean LC.50s for both diazinon and propetamphos showed a significant increase between seasons although th is is not necessarily indicative of a trend. Mean LC50S for diazinon i ncreased from 1.16 to 1.60 mg/1 (P < 0.001) and for propetamphos from 0.49 to 0.59 mg/l (P < 0.005) in pooled populations. Diazinon and prop etamphos resistance was significantly correlated in both seasons, sugg esting side-resistance between the two insecticides.