Hit by Hurricane Irma and a citrus ailment known as "Yellow Dragon Disease," Florida orange growers are bracing for potentially the worst harvest in more than a half century.

Forecasters are projecting a yield of 46 million boxes of oranges for the 2017-2018 Florida orange season, a drop of 33 percent from last year and the lowest output since at least 1944-1945, according to the US Agriculture Department.Some areas have lost as much as 90 percent of their fruit due to winds from Irma, or root damage due to flooding.

"It may take months for growers to gauge the true scale of the impact of Hurricane Irma and years to fully recover," said Shelley Rossetter, a spokeswoman for the Florida Citrus Department.

Florida oranges aren't the only casualty of 2017, an unusually busy year for natural disasters in North America.

The massive "Thomas" wildfire, considered the second biggest fire ever in California, has damaged lemon and avocado crops in the region north of Los Angeles.

Hundreds of acres of producing land have burned, said Ken Melban, vice president of industry affairs at the California Avocado Commission.

"It's a very unusual fire, some areas have been burned several times," Melban said. "It has a tremendous impact on growers impacted by the fire."

But Melban said it was difficult to determine the full impact on avocado prices because of higher imports and the supply from California growers not touched by the fire.

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But in Florida, where the orange industry employs 45,000 and an economic impact in the state of $8.6 billion, the outlook is grim, especially since the industry already faced myriad challenges even before Irma hit in September.

Citrus greening disease -- otherwise known as Yellow Dragon Disease -- is a bacterial malady spread by insects that has begun to ravage crops, killing some orange trees and rendering other fruit small and sour.

Orange production in Florida, which peaked at 244 million cartons in 1998, fell last year to 67 million.

There is no cure, so growers are focusing on ways to limit the spread of the disease, and on technologies and growing practices that could build resistant to the disease.

"Things were starting to turn around," Rossetter said. "Before Hurricane Irma, Florida Citrus growers were expecting 75 million boxes, the first crop size increase in years."

But she warned that in the wake of the storm, "Without support from state and federal government, some growers may go out of business."

The state orange industry also has come under pressure due to declining demand for orange juice as Americans turn to less sweet drinks and other alternatives. About 90 percent of Florida's oranges are used for juice.

US consumption of fresh orange juice has fallen 18 percent in just four years, according to Nielsen data.

At the same time, rising imports offer unwelcome competition. Brazil, a big producer of oranges for orange juice, could see an increase in output of 55 percent this year amid favorable weather conditions, according to USDA.