Dogs find citrus greening disease faster than humans

By Paul Brinkmann
A German shepherd detection dog finds an orange tree that is infected with citrus greening disease. Photo courtesy of F1K9/U.S. Department of Agriculture
1 of 2 | A German shepherd detection dog finds an orange tree that is infected with citrus greening disease. Photo courtesy of F1K9/U.S. Department of Agriculture

ORLANDO, Fla., Sept. 18 (UPI) -- Citrus growers in Florida, California and elsewhere have a new tool available to find devastating greening disease long before humans can spot it: dogs.

The dogs can spot the disease on trees years before lab tests can, and animals can be much cheaper than repeated laboratory testing, experts say.


"There's still no technology that matches a dog's sense of smell, which builds on millions of years of sensory development," said Tim Gottwald, a U.S. Department of Agriculture researcher in Fort Pierce, Fla., who led the project to train and test the dogs.

"They're essentially interrogating the trees as they go up and down the row, and they don't have to go back to the lab," Gottwald said.

He said he believes this is the first time dogs have been trained to detect the disease at such a high level of confidence that they can be deployed for commercial work.


Another USDA researcher, William Schneider, left his government post to help start a company to provide crop-sniffing dogs -- F1K9 LLC, based in Yalaha, Fla., not far from Orlando.

Impressive results

"The dogs were doing better than anything I could create with a machine," said Schneider, now chief science officer at the company.

Schneider said F1K9 has trained 20 dogs to detect the citrus greening, which results in reduced crop yields and leads to the death of trees infected with the Asian citrus psyllid.

Sometimes called jumping plant lice, the pest was first discovered in the United States on the east coast of Florida in 1998, according to University of Florida entomologists. The insects thrive by sucking plant juices.

There is no cure for the disease, which is assumed to be caused by a bacterium spread by psyllid infestation. That is why ridding groves of those trees as soon as possible is crucial.

"I think this can really help to contain the disease in California, and possibly in northern Florida, where there is enough winter to kill the psyllids occasionally," Schneider said. "We need more dogs trained to do this. Eventually, Florida might be able to plant new groves again."


Ruined business

The disease has left the once thriving Florida orange business in ruins, with crops recently reduced to one-quarter of historic highs. The state took a hit of $4.6 billion to its gross domestic product in a five-year period after the disease took hold in 2006.

In response, millions of dollars have been poured into fighting the disease, including $4.4 million from the USDA for the canine research project in recent years.

The dogs can test trees for about $4.50 per tree, according to F1K9. That compares to $20 or $30 per tree for lab tests.

That older method of testing was performed on individual leaves, which had to be chosen by field workers. That meant they could easily pull healthy leaves from a tree that had the disease, rendering lab tests erroneous.

Dogs, on the other hand, can smell the bacteria that causes the disease, even if the infection is just starting, F1K9 researchers said.

Big client signs on

The Ventura County Farm Bureau in southern California was among F1K9's first big clients. The dogs sniffed out fields where citrus greening was suspected. They found it, and hundreds of trees were cut down as a result but many more were saved.


"I'm convinced the dogs are detecting the presence of the bacteria that cause the disease, and the growers who are bringing the dogs in are, too," said John Krist, chief executive at the farm bureau. "We have to find the disease early. You can't do that with lab tests."

The dogs are mostly German shepherds or Belgian Malinois -- breeds that love to play so much that playtime is the only reward they need for finding sick trees.

"We have rubber Kong toys we use to let them play a little when they find a tree," Schneider said.

"We're not sure how far away the dogs can smell" the disease, Schneider said. "They are usually leashed by a handler. But we let them run free sometimes, and they will suddenly change direction and head directly for a specific tree."

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