Vegetable waste extracts as enhancers of baculovirus infections

Vegetable waste extracts (VWE) contain a great variety of antioxidants such as polyphenols, which have shown to potentiate baculovirus infections, making them ingredients for pest control ingredients. In the present study, the mortality enhancement of different vegetable extracts obtained from food residues when combined with baculoviruses was evaluated. Extracts from spent coffee (E2), rosehip (E17), asparagus (E28), artichoke (E29), beet stalks (E32) and banana peel (E37) were selected as they increased mortality of Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) in second instar S. littoralis larvae, when comparing with the virus inoculation alone. Extracts were assayed at 1 % w/v. In S. littoralis-SpliNPV system, the selected extracts reduced the median lethal concentration (LC₅₀) of SpliNPV against second instar larvae. The E37 extract presented the highest potentiation, as it reduced the LC50 13.61 times, while the rest of the extracts presented LC50 reductions from 3.71 to 7.72-fold. In Spodoptera exigua-SeMNPV (Spodoptera exigua multiple nucleopolyhedrovirus) system, none of the extracts decreased the LC₅₀ of SeMNPV. In contrast, in Spodoptera frugiperda-SfMNPV (Spodoptera frugiperda multiple nucleopolyhedrovirus) system, E2 showed the greatest potentiating effect. In the heterologous systems, none of the extracts tested increased the effective host range of SfMNPV, AcMNPV (Autographa californica multiple nucleopolyhedrovirus), and MbMNPV (Mamestra brassicae multiple nucleopolyhedrovirus) in second instar S. littoralis larvae. Thus, the viral enhancing effect of VWE was host-pathogen and instar dependent. However, the potentiation effect of the extracts could not be directly related with the antioxidants content of the extracts.