Evaluation of chemical treatments on pear, '70, '71

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.