Field trials of CpGV virus isolates overcoming resistance to CpGV-M

The Cydia pomonella granulovirus (CpGV) has been used for many years as biological agent for codling moth control in apple orchards. Resistance to the Mexican strain of CpGV was detected in orchards in Germany, France and Italy. A laboratory insect colony was started from insects collected in a French resistant orchard. It was named RGV. Various virus isolates were identified as active against this resistant insect colony. Field tests were carried out in 2007 to test if the two virus isolates CpGV-I12 and NPP-R1 were effective in the field. Although these virus isolates were not able to reduce insect caused fruit damages, they significantly reduced the overwintering insect populations. NPP-R1 was subjected to eight passages on RGV larvae (NPP-R1.8) that improved its biological activity on RGV larvae. 2008 field trials were set up to test this improved virus strain, compared to CpGV-I12 and Madex plus active on RGV. These tests confirmed the ability to control both in susceptible and resistant insect populations.