But for Florida’s struggling orange and grapefruit growers, the approvals could not come soon enough. The desperation is palpable across the state’s sandy midsection, a flat expanse once lushly blanketed with citrus trees, most of them the juice oranges that underpin a $7.2 billion industry employing 50,000 people, about 40,000 fewer than it did two decades ago. These days, the landscape is flecked with abandoned groves and scraggly trees whose elongated yellow leaves are a telltale sign of the disease.

Mr. Petteway says the antibiotics have helped bring many of his trees back to life.

“They used to have pneumonia, but now it’s like they have a cold,” he said, tugging on the waxy, bright green leaf of a tree thick with embryonic, gumball-size fruit.

[Read our series on antimicrobial resistance: Deadly Germs, Lost Cures]

A temporary approval of the drugs was issued under President Barack Obama, but in December, under President Trump, the E.P.A. gave final approval for a much broader use of oxytetracycline. The agency has also proposed the expanded use of streptomycin under similar terms.

The decision paves the way for the largest use of medically important antibiotics in cash crops, and it runs counter to other efforts by the federal government to reduce the use of lifesaving antimicrobial drugs. Since 2017, the F.D.A. has banned the use of antibiotics to promote growth in farm animals, a shift that has led to a 33 percent drop in sales of antibiotics for livestock.

The use of antibiotics on citrus adds a wrinkle to an intensifying debate about whether the heavy use of antimicrobials in agriculture endangers human health by neutering the drugs’ germ-slaying abilities. Much of that debate has focused on livestock farmers, who use 80 percent of antibiotics sold in the United States.

Although the research on antibiotic use in crops is not as extensive, scientists say the same dynamic is already playing out with the fungicides that are liberally sprayed on vegetables and flowers across the world. Researchers believe the surge in a drug-resistant lung infection called aspergillosis is associated with agricultural fungicides, and many suspect the drugs are behind the rise of Candida auris, a deadly fungal infection.