Baculovirus synergy: mixed Alphabaculovirus and Betabaculovirus infections for the control of Thaumatotibia leucotreta in South Africa

Abstract: The recent identification of a nucleopolyhedrovirus (NPV) capable of establishing infection in three major pests, namely Cryptophlebia peltastica (litchi moth), Thaumatotibia leucotreta (false codling moth) and Cydia pomonella (codling moth) provides an opportunity for improved methods such as synergism for control of agricultural pests in South Africa. Genetic characterisation identified the NPV as Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), a newly identified Alphabaculovirus. In this study, we report the development of a multiplex PCR assay which can distinguish Cryptophlebia leucotreta granulovirus (CrleGV) and CrpeNPV in mixed samples. Furthermore, the biological activity of CrpeNPV and CrleGV-SA against FCM larvae was evaluated both in isolation and in combinations at ratios of 3:1 and 1:3. The LC50 values for all treatments varied only slightly, ranging from 7.95 × 104 to 1.23 × 105 OBs/ml. At the LC90, a combination of CrleGV and CrpeNPV showed a three- to four-fold improvement in virulence compared to pure viruses. Trials are currently underway to evaluate the effect of mixed CrleGV/CrpeNPV applications under field conditions.