Overwinter transmission of CpGV on infected diapausing larvae

Abstract: Different granuloviruses are used as biological control against insect pests. Among them, Cydia pomonella granulovirus (CpGV) is widely sprayed in apple orchards to limit codling moth proliferation. Resistance to CpGV-M has developed in some European orchards. A better understanding of the biology of the virus should allow a better rational use leading to increased durability of this control method.Transmission of CpGV from one year to the next in natural conditions relies in the presence of reservoirs in orchards, allowing young larvae of the first generation in the spring to enter in contact with the virus. A possible way is the survival over winter of infected larvae that could die upon metamorphosis or yield infected adults able to vertically transmit the virus.We have explored using qPCR the level of infection in overwintering five instar codling moth larvae that survive to the late summer treatments in commercial orchards. About 8% of such larvae were found to be positive for virus.