County agriculture officials found frost damage Monday in all but one of 19 citrus samples gathered from across Kern County on Friday, raising fears of widespread financial losses for local growers.
Regulators and industry people say the freeze has only worsened in the three days since, and they expect damage to be worse when they test again later this week.
"It's not a total crop loss, but there's enough damage that it'll have some impact," said Al Bates, Central Valley general manager at Sun Pacific, which owns 20,000 acres of mandarins in the region.
In preliminary testing from Friday, mandarins suffered the worst, with half of the six samples tested showing enough damage to write off an entire block of 20 to 40 acres of fruit. There are between 30,000 and 40,000 acres of mandarins in the Central Valley.
One of eight navel orange samples displayed substantial damage, while lemons appear to have escaped serious damage, a county official said. One sample consists of 33 individual pieces of fruit.
More samples are to be gathered Tuesday for testing Friday. More extensive sampling is tentatively set for next week.
The National Weather Service has declared a hard freeze warning in the area through Wednesday morning, meaning temperatures 28 degrees or below are expected to last for up to eight hours at a time. Such weather can be devastating for citrus.
While Kern's urban areas dropped to the upper 20s Monday morning, outlying areas fell to 21 degrees or colder, said Jim Dudley, a meteorologist at the NWS' Hanford office.
Temperatures were forecast to be only slightly warmer Tuesday morning. A general warming trend was not expected to arrive until Thursday. No precipitation is predicted in the foreseeable future, Dudley said.
Sunday's and Monday's cold weather brought new pessimism -- not necessarily because of how cold it got but how long the mercury remained below the critical point of 28 degrees.
Paul Story, director of grower services for the trade group California Citrus Mutual, said most Valley citrus growers are worried about having damaged fruit. But he said nobody knows the extent yet.
"I don't think it's a catastrophic event in terms of the fruit loss on the navels. We think there's more loss on the mandarins," he said.
Monday's citrus tests consisted of county staff slicing open fruit and looking for signs that juice sacks have ruptured during freezing, leading to drying and rendering the fruit worthless. The tests were conducted by the office of the county Agricultural Commissioner, which is responsible for inspecting fruit and determining whether it is damaged enough to throw out an entire batch.
Since last week, Kern growers have been using water, wind machines and helicopters to raise temperatures and avoid losses. The citrus trade group estimated Sunday that such efforts have cost Valley citrus growers $17.5 million since last Tuesday.
Roughly 80 percent of the Valley's $1.5 billion citrus crop remains to be harvested, the associated estimated. In Kern, citrus is the county's fourth most valuable category of crop behind grapes, almonds and milk.