Optimization of Large-Scale Production of Chrysodeixis includens nucleopolyhedrovirus for Its Use as a Biopesticide

The baculovirus Chrysodeixis includens nucleopolyhedrovirus (ChinNPV) is pathogenic to Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae) larvae, known as soybean looper, which is an important pest of soybean and bean. In this study, some parameters were tested to overcome the difficulties in the in vivo production of ChinNPV aiming to increase its use as a biopesticide. First, different combinations of larval instars (3rd and 4th instars), larval incubation temperatures (23 °C and 26 °C), and rearing densities (individually and 10 larvae/cup) were compared for larval weight and the production of occlusion bodies (OBs). A positive correlation (p< 0.001) was observed for OB production and larval weight. Fourth instar larvae produced more OBs than third instar larvae (p<0.05); however, no significant differences in OBs/larva (p>0.05) were observed for larvae kept in groups or individually. Therefore, a second assay was performed using fourth instar larvae incubated at 26 °C and two larval densities (10 larvae/cup and 40 larvae/cup). The losses of insects and OB production were evaluated as well as the influence of storage temperatures post-mortem (-20 °C, 4 °C, and 15 °C) in the OB yield. As expected, insect losses due to cannibalism or microbial contamination were greater (p<0.05) with the increase in larval density, although no difference was observed in OBs/larva (p>0.05). In addition, the storage temperature post-mortem did not influence the OB yield (p>0.05). The average production of ChinNPV OBs was 3×10¹⁰ OBs/40 larvae cup. The results demonstrate the viability of rearing C. includens in groups to enhance the mass production and reduce virus production costs.