Temperatures reached as low as 26 degrees in unprotected areas of Madera, Fresno, Tulare and Kern counties over three nights Dec. 18-20, said Bob Blakely, director of industry relations for Exeter-based California Citrus Mutual.
In groves growers ran frost protection measures – wind machines and watering – to keep temperatures several degrees higher.
“The biggest threat this week was to the mandarins which are not as cold-hardy as the navels,” Blakely said. “This was not a serious event at all for oranges. If the mandarins had not had protection, it could have been pretty serious. But as it was the water and wind machines did a good job. The worst case is very minor damage to no damage.”
Any damage to mandarins on the edges of protected areas might not show up until February or March.
High sugar content in this year’s crop plus mild weather earlier on proved helpful, Blakely said.
“There’s really good sugar in the fruit right now and the higher sugar lowers the temperature the fruit can withstand,” he said. “And because we’ve had relatively warm weather up until now the internal temperature of the fruit was not as low as it would have been had we had three or four weeks of really cold nights.”
“One grower told me he didn’t really need to run the wind machines for his oranges on the first night but he did as a test to be sure everything was working,” Blakely said.
As of Dec. 21, no additional freezes were forecast.