Panicle blanking, or the occurrence of “empty” kernels” on the rice panicle, may have caused yield losses of up to 12.5 per cent in 40 rice fields grown for certification in 1971. Although varieties differ in susceptibility to blanking, causes other than resistance appear to be responsible for the range in panicle blanking from 3.81 to 25.46% in different fields. Low night temperatures during pollen formation are believed to be the major cause of blanking. Pollen formation occurs during a 5-day period about 10 to 16 days before heading. Further studies aimed at finding solutions to this problem are in progress.

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This research was partially supported by a grant from the Rice Research Board, California Department of Agriculture. Jack DeWitt, Rice Growers Association, Sacramento, assisted in collecting field samples.