One of the key factors of progress of an epidemic is the duration of virus availability for a vector in plants, which could be influenced by temperature. Using five epidemiologically different isolates of Plum pox virus (PPV) we studied the effect of temperature on the virus infectivity, intensity of disease symptoms and virus accumulation in Nicotiana benthamiana plants as determined by a double-antibody sandwich-enzyme-linked immunosorbent assay (DAS-ELISA). No differences in infectivity and intensity of disease symptoms between the five isolates were observed at 17 degrees C. However, they differed in their capacity to infect and multiply in the plant at higher temperatures. The temperature of 32 degrees C was inhibitory to the multiplication of all the five PPV isolates studied. Fewer plants were infected and a significantly decreased amount of virus antigen was detected at 30 degrees C. The natural PPV recombinant BOR-3 isolate showed a greater temperature tolerance compared to other PPV isolates tested. We conclude that adaptation to higher temperatures may favour the epidemiological impact of PPV.