Use the insiders: could insect facultative symbionts control vector-borne plant diseases?

Insect vector-borne plant diseases, particularly those whose causative agents are viral, or phloem- and xylem-restricted bacteria, greatly impact crop losses. Since plants are immobile, the epidemiology of vector-borne diseases greatly depends on insect vectors, which are the only means of dissemination for many pathogens. The effectiveness of a vector-borne pathogen relies upon the vectorial capacity, which is affected by vector density, feeding activity on hosts, longevity before and after pathogen ingestion, duration of the incubation period, and vector competence. During the last decade, research on human vector-borne epidemics has stimulated interest in novel control strategies targeting different parts of the vector cycle, and our purpose here is to draw parallels between this field of research and agronomy. We review the literature on insect vectors of crop diseases and their symbiotic microorganisms with the aim of suggesting future integrated management techniques based on current research on insect-vectored human diseases. Vector transmission is a complex process and different modes of transmission are encountered irrespective of the pathogen. Facultative symbionts have varied effects on life history traits that could be used for vector population control. Symbiont selection, transformation, and their manner of dissemination are important when developing an integrated vector management system based on symbiont manipulation. In the short term, progress on our knowledge of the microflora of insect vectors of plant diseases must be made. In the long term, symbiont manipulation, which has been successfully demonstrated against human insect-vectored diseases, could be adapted to insect-borne plant diseases to increase sustainable crop production.