Effect of temperature on long-term storage of Cydia pomonella Granulovirus (CpGV-M)

Abstract: Codling moth (CM) is the major pest in apple and pear production worldwide. The application of Cydia pomonella granulovirus (CpGV) products is an ecologically safe alternative to chemical treatments to control CM. In this study the long-term activity of occlusion bodies (OBs) of the commonly used CpGV-M isolate, stored at room temperature (RT), +4 °C, -20 °C, and -80 °C for five years was assessed. Median lethal concentration (LC50) of the tested OB suspensions was elucidated in full-range bioassays with neonates of the susceptible CM strain CpS after seven and 14 days. The LC50 values at +4 °C, -20 °C and -80 °C storage temperature were between 225 OBs/ml (4 °C) and 7991 OBs/ml (-20 °C) after seven days and comparable to the LC50 determined at the beginning of the storage test (LC50 1871 OB/ml). Only the virus-induced mortality of OBs stored at RT decreased that the LC50 could not be determined. This research indicates that the storage of OBs of CpGV-M at 4 °C or colder will ensure the bioactivity for at least five years.