Monitoring resistance to diflubenzuron and deltamethrin in French codling moth populations (Cydia pomonella)

French populations of codling moth have developed resistance to several insecticide classes, The susceptibility of susceptible and resistant laboratory strains to diflubenzuron and deltamethrin was evaluated using different exposure methods against various Life stages. The tarsal contact method for adults was found to be an appropriate method for testing neurotoxic compounds such as deltamethrin. Insect growth inhibitors, like diflubenzuron, need to be analysed on Juvenile instars. Monitoring methodologies were developed and evaluated (a) on neonates obtained by crossing field-collected males with virgin females from the susceptible laboratory strain so as to overcome the problem of reduced fertility of wild females and (b) on diapausing larvae. All 36 populations analysed exhibited significant levels of resistance to both diflubenzuron and deltamethrin, Resistance to the two compounds was linked, regardless of the cultivation methods used in the monitored area. The monitoring methodologies will be implemented to evaluate the evolution of resistance according to the resistance management strategies that have been adopted. (C) 2000 Society of Chemical Industry.