Abstract Description

Thaumatotibia leucotreta is an important pest to the South African citrus industry, costing it millions of Rands annually. The pest is currently controlled using an Integrated Pest Management (IPM) approach in which baculoviruses play a crucial role. Commercial products like MutiMax (River Bioscience, South Africa), contain Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV) as an active ingredient for the control of Thaumatotibia leucotreta and Cydia pomonella. Products like Codlgran (River Bioscience, South Africa), contain C. pomonella granulovirus (CpGV) and are also used to control C. pomonella populations. Additionally, CpGV is known to infect T. leucotreta, although it is not used for the control of this pest. These products are already commercially used in South Africa while MultiMax will soon be available in Europe. Considering the shared host range, it is important to evaluate the effects CrpeNPV and CpGV have on one another during mixed infection should products containing both viruses be applied on or near the same fields. Surface dose biological on T. leucotreta showed CrpeNPV to have a LC50 of 4.43x10^4 OBs/ml. This showed it to be significantly more infectious to the host compared to CpGV, with an LC50 of 2.28x10^6 OBs/ml. Mixed infection bioassays have indicated antagonism between the two viruses. Larval mortality dropped from 48.6 % when exposed to CrpeNPV (LC50) alone to 19.4 % when larvae were exposed to a mixture of CrpeNPV (LC50) and CpGV (LC10). With these findings, the mixing of commercial biopesticides containing these viruses as active ingredients can be discouraged, potentially improving the control of T. leucotreta and other lepidopteran pests like C. pomonella.