AVON PARK, Fla. — Florida’s citrus industry is grappling with the most serious threat in its history: a bacterial disease with no cure that has infected all 32 of the state’s citrus-growing counties.

Although the disease, citrus greening, was first spotted in Florida in 2005, this year’s losses from it are by far the most extensive. While the bacteria, which causes fruit to turn bitter and drop from the trees when still unripe, affects all citrus fruits, it has been most devastating to oranges, the largest crop. So many have been affected that the United States Department of Agriculture has downgraded its crop estimates five months in a row, an extraordinary move, analysts said.

With the harvest not yet over, orange production has already decreased 10 percent from the initial estimate, a major swing, they said.

“The long and short of it is that the industry that made Florida, that is synonymous with Florida, that is a staple on every American breakfast table, is totally threatened,” said Senator Bill Nelson, a Florida Democrat who helped obtain $11 million in federal money for research to fight the disease. “If we don’t find a cure, it will eliminate the citrus industry.”