Abstract:
Brown rot caused severe losses on the Murrumbidgee Irrigation Areas in nine of 36 seasons. Slight to moderate losses were more frequent. The influence of weather on incidence of brown rot losses was examined. Losses did not occur unless there was rain when fruits were ripe. Losses never resulted from long damp periods occurring prior to the commencement of harvest. Rain causing surface wetness on ripe fruit of duration in excess of 10 hr was necessary before losses occurred. Severity of losses increased with duration of wetness, losses being most likely and most severe when the duration of surface wetness approached or exceeded 20 hr. The probability of losses increased with increasing number of long rain-induced damp periods during the harvest period. Dews appeared to have little influence on brown rot incidence. Temperatures during damp periods were generally in a range suitable for infection. The most common weather patterns associated with long rain-induced damp periods are described. Losses from fruit rot increase for some 3-5 days after the damp period causing infection, then gradually decline. Springtime brown rot infection was not a prerequisite for fruit rot.