Resistance to Cydia pomonella granulovirus follows a geographically widely distributed inheritance type within Europe

The Cydia pomonella granulovirus (CpGV) is an important agent for control of the codling moth C. pomonella (L.). Since 2004, cases of resistance to CpGV products have been found in codling moth populations of several apple plantations in Europe. Recently, the first codling moth population (Cp-VBII) with reduced susceptibility to CpGV was found in the Czech Republic. The F1 offspring of Cp-VBII collected in different years were tested for CpGV resistance at a diagnostic concentration of 3 × 10⁵ occlusion bodies (OBs) ml⁻¹ and showed reduced mortality. The strain CpR-CZ with a genetically fixed resistance was selected from Cp-VBII and showed no mortality at the diagnostic concentration. Single pair crossing experiments demonstrated that the resistance of CpR-CZ is dominantly inherited and linked to the sex chromosome Z. New CpGV isolates (CpGV-E2, -I08, -I12, -S, and -V15), and two new CpGV products (Madex Plus^® and experimental product ABC V15) had a satisfactory efficacy against CpR-CZ neonate larvae. These results indicate that CpGV resistance becomes apparent under CpGV selection and argues for its geographically wide distribution and independent emergence within Europe.