| Popis: |
The different aspects involved in the transmission of phytoplasmas by insect vectors (leafhoppers, planthoppers, and psyllids) are presented from an ecological point of view. The epidemiology of phytoplasma-associated diseases is a consequence of the vectors’ ability in acquisition, inoculation, dispersal, survival, host range, and habitat colonization. Within the same vector species, acquisition efficiency may depend on the phytoplasma load in source plants and on the vectors’ life instar (nymphs versus adults). Inoculation may occur earlier or later in the season, depending on the availability of phytoplasma sources and/or possible presence of transovarial transmission. Monophagous and oligophagous species are generally more efficient vectors than polyphagous ones. Among grass feeders, many vector species are considered oligotopic. Ecotones, plant patches, and plant architecture affect the movement and survival of vectors. Vectors’ flight activity and spatial distribution, which may differ depending on gender, affect the spread of phytoplasmas and their epidemics may follow an open or a closed cycle. Five examples of diseases, with different phytoplasma cycles (open/closed) and one or more insect vectors involved, are presented: grapevine “flavescence doree”, Palatinate grapevine yellows, grapevine “bois noir” and maize redness in Europe; aster yellows in USA; sugarcane white leaf yellows in South-East Asia; and coconut lethal yellowing in North and Central America. |
