Can biological control be a strategy to control vector-borne plant viruses?

Abstract

Plant viruses transmitted by vector pests are one of the most important worldwide threats to global food production and security. Biological control strategies to enhance natural enemies (parasitoids and predators) have mainly focused on their ability to reduce pest density. In contrast, few studies have examined how natural enemies affect the spread and the incidence of viruses in a crop, although those results could be used as levers for a more sustainable management of viral diseases. Vector-borne plant viruses can be classified in three categories based on their transmission mode: non-persistently transmitted viruses, semi-persistently transmitted viruses and persistently transmitted viruses, whereas vector density, fitness and movement were identified as main drivers of virus spread in a crop, their relative contributions to virus epidemiology may also depend on both the transmission mode and the presence of natural enemies. The first part of the review focuses on virus transmission dynamics in relation to vector activity and density. Because we identify different patterns for each type of plant viruses, control strategies that lead to changes in vector traits, should be adapted to the targeted virus. However, biological control of insect vectors has been rarely adapted to the mode of transmission of the target virus. Thus, the last part of the review explores the conditions required for natural enemies (parasitoids and predators) to prevent epidemics outbreaks of each type of plant viruses. Briefly, if combined with other practices, biological control of vectors to keep virus incidence below the economic threshold is a promising approach for persistently transmitted viruses but might be more difficult to achieve with non-persistently transmitted viruses and semi-persistently transmitted viruses.