The efficacy of a CpGV-based preparation of Czech production against codling moth (CM) was tested in an experimental apple orchard at Prague-Ruzyně in 1998-2000. The influence of CpGV treatment on the reduction of CM population density and fruit injury was evaluated in comparison with teflubenzuron. Decline of CpGV efficacy in the orchard was tested in laboratory conditions on apples sampled at different terms after CpGV treatment. The rates of CpGV applied ranged from 0.5 to 1.00 × 1013 granulles/ha, and the number of applications from 3 to 5 per year. The biological efficacy of CpGV to reduce the CM population density ranged from 75.5% to 96.0%, that of teflubenzuron from 90.8% to 97.5%, compared to the untreated control. The CpGV treatment was more efficacious in reducing the CM population density than in reducing fruit injury. The efficacy of CpGV decreased to 50% after 20, 10 and 11 d after treatment in 1998, 1999 and 2000, respectively. According to our results, a 10 d interval for CpGV treatments is recommended in case of further mass egg-laying by CM in the period between CpGV applications.