Meet the disease-sniffing dogs out to save Florida’s orange crop from a deadly bacteria

Mira’s nose is really sensitive that they can smell sick citrus trees, and U.S. orange growers are hoping her super sniffer can help combat one of the biggest threats ever for their crop.

The government has trained 10 dogs including Mira – a 32- month-old German Shepherd-Belgian Malinois mix – to recognize a bacteria that has been killing citrus trees for a decade in Florida, the biggest domestic producer. Much like canine teams that sniff out bombs, drugs as well as bed bugs, this one is searching for any disease referred to as citrus greening. There’s no cure, but growers hope the animals will give them additional time to find one by slowing the contagion.

Florida’s orange harvest is forecast to reach a 52-year low this season, down 71 per cent since 2004 as tiny bugs called Asian citrus psyllids spread the bacteria. It cost the citrus industry US$7.8 billion and seven,500 jobs since 2006. Dogs, with 50 times more scent receptors in their noses than humans, sense chemicals that trees emit when infected. They’re accurate 99.7 per cent of times – much better than laboratory tests – and identify diseased trees before symptoms appear.

“They’re virtually the forefront of early detection for us right now,” said Yindra Dixon, a public affairs specialist for the Animal and Plant Health Inspection Service, one from the U.S. Department of Agriculture.

While researchers have didn’t look for a remedy for the disease, also known by the scientific name Huanglongbing, they devised ways to slow its spread. One technique requires farmers to encase trees in steam to overheat the bacteria without killing the plant. Some apply nutrients on the leaves to help keep trees productive even as they’re dying. Others use more pesticides to kill the psyllids, but the downside is the bugs developed resistance to some chemicals and an excessive amount of can burn the fruit. Penicillin can suppress the bacteria, but concerns over antibiotic resistance have limited wider use.

Citrus greening blocks the passage of nutrients through the tree’s vascular system, resulting in the plant to thin and yellow. Trees may take years to die, but their fruit production declines and finally is too promising small to justify the fee for treating the symptoms.

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Fewer Oranges

Florida is expected to reap 69 million boxes of oranges this season, or 56 percent of domestic production, and the state may be the top grower of grapefruit, USDA data show. Each box weighs 90 pounds. California will supply 52.5 million boxes of oranges, and it is the dominant supplier of tangerines and lemons. Texas ranks second in grapefruit.

Since 2005, once the disease was first based in the U.S. in Miami-Dade County, 15 states or territories have been placed directly under full or partial quarantine for the existence of the Asian citrus psyllid. 



The bugs, which transmit the bacteria, reproduce rapidly and may fly a mile without pause, which makes them especially difficult to contain or kill. Researchers continue to be attempting to understand how psyllid populations reduced by pesticides still have the ability to recover and spread the disease, said Robert Shatters, research molecular biologist for the USDA Horticultural Research Laboratory in Fort Pierce, Florida. As the disease exists in other countries like Brazil, the world’s biggest orange grower, the flat landscape and close proximity of farms in Florida allow it to be particularly prone to contamination.

“This can be a disease where your neighbour is your worst enemy,” said Thomas Spreen, professor emeritus of food and resource economics at University of Florida in Gainesville. 

Early Detection

Already, about 75 percent of Florida’s groves are infected. The USDA is likely to dispatch most of the new canine unit to California, Arizona and Texas, in which the disease is less widespread and early detection might be used more broadly, Dixon said.

This is a disease where your neighbour is your worst enemy

“There’s such a grave concern in areas where this ailment does not exist that people want to know if it’s there,” said Tim Gottwald, research leader and plant pathologist at the USDA.

Training dogs to detect citrus greening was funded through the Huanglongbing Multi-Agency Coordination Group, an urgent situation response team developed by the USDA in 2013 to determine how you can eradicate the disease. The MAC invested US$1.8 million of their US$20 million research plan for 2014 and 2015.

More Accurate



Tests show the wet noses from the dogs tend to be more accurate than DNA sampling techniques, which could require several hours or days to accomplish and therefore are susceptible to lab-related and sampling errors, Gottwald said. The animals also provide detected the disease in trees that didn’t show symptoms until days or weeks later, he said.

Once trained, Mira and the other dogs show they are both eager and accurate, said Jerry Bishop, the training director at Coast to Coast K9 Teams, the company dealing with the USDA to coordinate grove inspections by the animals.

“When she comes out from the kennel, she likes to chest bump you,” Bishop said of Mira. “She’s like, ‘Let’s go to work. I’m ready.’”

Spreen, the emeritus professor, says the dogs offer a potential cheap and efficient bit of hope for growers faced with devastating losses.

Even when the dogs aren’t 100 percent accurate, “you can probably suppress the infection enough inside your grove to actually make a huge difference,” said Spreen, the master of 19 acres of citrus groves. “The dogs could potentially be a godsend.”

— With assistance from Marvin G. Perez.

Bloomberg News