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

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