Fireblight, caused by the bacterium Erwinia amylovora, was more severe in Sacramento Valley pear orchards during 1970 than any time in the previous 20 years. Following the warm winter of 1969-70, the regular pear bloom was prolonged for approximately a month with first bloom March 16 and petal fall ending in mid-April. “Rat-tail” (late season) bloom continued for several weeks during May and June. During much of this period, weather conditions favoring blight were ideal with temperatures over 65°F, and frequent rains. First widespread fireblight infections were observed in the Sacramento Valley between April 18-21, continuing through May and June.