INTERACTION OF TEMPERATURE AND MOISTURE ON INFECTION OF WILD-RICE BY BIPOLARIS-ORYZAE IN THE GROWTH CHAMBER

Infection of wild rice (Zizania palustris) flag leaves by Bipolaris or yzae was studied at temperatures of 5 to 35 degrees C and wet periods of 2 to 36 h after inoculation. Lesion densities (lesions/cm(2)) incre ased with increasing wet periods depending on optimum temperature. Hig h rates of infection occurred at 25 and 30 degrees C and generally inc reased with continuous wet periods of 16, 18, 24, and 28 h. There were no lesions at 5 degrees C and few at 10 and 35 degrees C. Lesion dens ities declined when wet periods of 2, 4, or 6 h were interrupted by dr y periods of 4, 6, 8, 10, or 12 h followed by a final 14 h of wetness. Lesion densities decreased at all temperatures with increased dry per iods regardless of the initial wet period. The interaction of dry peri od length x wet period length x temperature was significant at the 0.5 % level. With continuous wet periods, lesion numbers were highest at 2 5 to 30 degrees C.