In autumn when the water temperature
falls to below 20 °C, adductor coloring starts to fade,
which is followed by a rapid decline in mortality (Wada,
1999). By experimentally analyzing the effect of water
temperature on red adductor disease, we found that no
disease onset was observed below 16 °C, and that the
incidence at 19 °C was under 5%. On this basis we
concluded that water temperatures below 19 °C effectively
contain clinical outbreaks of the disease, which
coincides well with previous reports It therefore appears that the lowest temperature at
which infected pearl oysters contract the disease is
approximately 19 °C. Experiments at 19 °C to 31 °C
showed that high temperatures may promote development
of clinical signs, which suggests that 19 °C is a
benchmark to watch for disease onset.