When -- or if -- that bunch of flowers arrives on Sunday for Valentine's Day, spare a thought for Edward Putland.

Putland, an agent specializing in agriculture at US Customs and Border Protection (CBP), has been busy scouring roses, carnations and all other manner of flowers and plants imported through Miami's international airport, mainly from Latin America.

For Putland and his fellow inspectors the first half of February presents a daunting challenge: about a billion flowers and plants pour into the US during the three weeks leading up to Valentine's Day on February 14, of which more than 90 percent comes through the Miami airport.

They are on the lookout for diseases or insects that could wreak havoc on the floral and agricultural industries in the United States.

"I just found some egg masses on the leaves. I'll send them to the USDA for identification," Putland tells AFP, referring to the Department of Agriculture, after closely inspecting a cargo of palm leaves from Costa Rica.

His list of foes is long.

"Any kind of pest, any kind of insects may be in the shipments, anything -- diseases, all sort of insects, mites, lepidoptera, beetles, almost anything," he says.

"I usually find something every day, but sometimes it's something that we already have here in the US so we don't take action," he adds.

"But sometimes we do find something that we don't have and we don't want to get here so they have to take action on the commodity."

That means it gets tested and safely discarded.

This type of inspection requires a keen eye -- and a magnifier -- because sometimes the threat on the import is tiny.

The detective work is done in a refrigerated area in the airport's cargo section to prevent damage to delicate flowers.

- Multibillion-dollar industry -

Tulips, roses of all colors, exotic tropical flowers. Box after box, the merchandise keeps coming -- and so does the work.

The flowers mainly come from Colombia, which exports nearly 700 million flowers to the US for Valentine's Day, followed by Ecuador, Mexico, the Netherlands and Costa Rica.

Next to Putland, inspector Wilnette Perez carefully checks bouquets of red roses, starting with the petals and the stem.

Then Perez takes the flowers and taps them over white paper to see if any hiding insects pop out.

One slip or miss can have a devastating long-term impact far beyond the chaotic confines of the airport.

"We don't want the farmers to have to deal with a new pest in this country and the pest can cost a lot of money for our own agriculture," says Putland.

Underlining that threat, during the last Valentine's Day season nearly 1,500 cases of disease or insects were picked up at the Miami airport in batches of flowers or plants.

The inspectors' work is also vital because the flower industry in the US generates $15 billion a year and thousands of jobs are riding on it.

"Invasive species have caused actually, around the world and here, billions of dollars in economic and environmental losses," says Gil Kerlikowske, CBP commissioner.

"About 200,000 people throughout the United States depend on imported flowers for their business and their livelihoods, and of course 91.5 percent of fresh-cut flowers arrive in through Miami International Airport, so to have that level of responsibility is important."

That means the army of 2,400 CBP inspectors cannot rest or even miss a beat before Valentine's Day on Sunday.

And then they will do it all over again for Mother's Day in May.