First Evidence of CpGV Resistance of Codling Moth in the USA

Codling moth (Cydia pomonella L.) is a very important pest in apple, pear, and walnut
orchards worldwide, including the USA. Cydia pomonella granulovirus (CpGV) is used to control
codling moth in organic and conventional production. Due to increasing codling moth infestations
from organic apple orchards in Washington State, USA, five codling moth colonies (WA1-WA5) were
screened for their susceptibility relative to the isolate GV-0001, the main active ingredient of Cyd-X®,
using a discriminating concentration of 6 104 OB/mL. Compared to a susceptible laboratory colony,
the observed results indicated that GV-0001 lacked efficacy against codling moth colony WA3. It
was confirmed thatWA3 was the first case of codling moth resistance to CpGV in the USA. Further
testing of WA3 was performed on a range of CpGV isolates and a lack of efficacy was observed
against additional isolates. However, three newly developed CpGV preparations can efficiently infect
larvae from the resistant colony WA3. Our results suggest that there is an urgent need to monitor
the situation in the USA, aiming to prevent the emergence or spread of additional codling moth
populations with CpGV resistance. Strategies to sustain the efficacy of codling moth control using
novel CpGV formulations need to be developed.