Investigations on the mechanism of CpGV resistance in Cydia pomonella

After the successful use of CpGV in control of codling moths in organic and integrated farming for decades, some populations of Cydia pomonella developed resistance against CpGV products. Resistant populations were detected in several orchards in Germany, France, the Netherlands, Italy and Switzerland. The resistance is dominant, monogenic and sex-linked inherited. Beside the knowledge of heredity, it is mandatory to know the mechanism of resistance for the development of successful resistance management strategies. Three different experimental approaches were followed to investigate the mechanism involved in CpGV resistance: First, virus replication in three different tissues of susceptible (CpS) and resistant (CpRR1) insects was estimated by quantitative PCR. Second, humoral and cellular immune responses as a reason for resistance were investigated by transfusion of haemolymph from resistant into susceptible insects. Third, by-passing the midgut budded virus was directly injected into the insect’s haemocoel in order to investigate whether resistance is present in others than midgut cells.