The 58,000-pound mechanical harvesters pounding through groves outside Immokalee this spring gave a good look at the citrus industry’s possible future.

The ultimate winner may or may not look like them — but these are anything but test machines.

On a good day, the Oxbo harvesters manufactured at Clear Lake, Wis., team in a pair, running along each side of a row of trees, then come in with 14 loads, replacing four 20-man harvest crews, says their inventor and operator, Tom Visser.

An Australian, Visser has worked in Florida since 1993 to develop an effective citrus harvester.

Interest in mechanical harvesting of citrus goes back much further than that, however, at least to the 1950s. Whenever labor concerns peak, so does interest in mechanized harvesting, and the current immigration crisis that threatens to pinch the supply of citrus harvest workers has ramped up interest in the machines, although actual usage of the mechanical harvesters declined this year.

“Mechanical harvesting is absolutely feasible and economically necessary,” says Fritz Roka, University of Florida ag economist working at Immokalee. “We’ve documented that it saves money.

“Growers using it are showing that it saves 25 cents to 30 cents per box, even with the added cost of gleaning behind the machines. Growers of sound mind aren’t going to leave a single fruit out there; they will go back and get that 5 percent left in the grove.”

Growers concerned that mechanical harvesting stresses trees, making them more vulnerable to citrus greening disease, may have a valid point if the trees are already hurting, Roka says. He says that could be the reason some growers didn’t use the harvesters this year.

“We’ve got to bring these trees back to a healthy state. Research has documented over and over that whatever damage is done, a tree can rapidly overcome it and come back with a good crop the next year. The research is pretty good that the machine doesn’t adversely impact long-term tree health, if the tree is in good health to begin with.”

The machines add efficiency to harvesting at Cooperative Producers, Inc., groves near Immokalee and LaBelle. The co-op uses them to pick Valencia oranges, and is concluding three years of tests with an abscission compound that is likely to be paired with the machines, further increasing efficiency.

The mechanized harvest unit requires four trucks, or ‘goats’ — two with each machine. The machines, if purchased, would run about $1.3 million.

“With that kind of expense for the machines, you’ve got to run them,” Roka says. “You have to fill a lot of trailers to make them efficient. Anytime they’re interrupted, that puts a lot of pressure on these machines.”

They can be moneymakersin many situations. “How that efficiency equates to us, since we’re using a contractor, is that we had about a 30 percent savings over conventional harvesting,” says Mike Murphy, chief executive officer and executive vice president of Cooperative Producers.

After testing that began in the 1970s, the abscission chemical may finally be cleared in time to use it on the 2013 Valencia crop. The U.S. Environmental Protection Agency now has the compound under review and is expected to make its decision public in February.