Assessment of control strategies against Cydia pomonella (L.) in Morocco.

The codling moth, Cydia pomonella (L.), is the key pest of apple production worldwide. In Morocco, there is a sustainable presence of codling moth causing considerable damage in apple orchards despite frequent applications of broad spectrum insecticides. For 12 years, sexual trapping and chemical control were performed and the development of the codling moth population was analysed in an orchard which was in the region of Azrou. The efficacy of some insecticides (azinphos-methyl, chlorpyriphos-ethyl, diflubenzuron, thiacloprid, methoxyfenozide, spinosad, and deltamethrin) was also evaluated on neonate larvae and compared with a laboratory sensitive strain. This procedure was done to assess an eventual resistance in Moroccan populations. The action threshold was usually exceeded, leading to an intensive chemical control, with an average frequency of 9 to 13 days. The chemical control was done according to the action persistence time of the insecticides and the trap captures. However, those two parameters are compromised in Moroccan conditions because of the high summer temperatures which disrupt the action of insecticides and exacerbate populations. The pheromone traps may become ineffective and useless. Neonate larvae were resistant to five insecticides out of seven. Such results suggest the presence of a cross resistance in local strains. Overall, the insect resistance, the functioning of the sexual traps, and some insecticides properties (persistence action, pre-harvest interval) are the key factors that could explain the failure to control these moths under Moroccan conditions. [ABSTRACT FROM AUTHOR]