It is 10 years and more that a deadly and relentless epidemic of Xylella fastidiosa (a bacterial plant pathogen) has been destroying the olive trees of Southern Italy. An unprecedented catastrophe, which seriously damaged an entire sector. Perhaps we can begin to solve the problem with the help of a trusted friend: the best man has ever had.
In Parabita, in Puglia, a task force of highly qualified dogs and trainers was born, which deals with the detection of Xylella: it is called Xylella Detection Dogs. And it could not have been born elsewhere: Puglia, with its 60 million olive trees, was responsible for approx 50% of the production of olive oil in Italy. In just a few years, Xylella infected and killed 21 of these 60 million trees, many of which were genuine secular monuments.
Nicholas DiNoia he is an agronomist and general manager of Unaprol, the largest Italian consortium of olive oil producers. He fully understands the seriousness of the danger posed by Xylella and actively works to contain its spread. "This is an unprecedented ecological and environmental disaster," he says. "We can't get carried away by environmentalist emotions, we have to rely on scientific data." In 2020, Di Noia looked back on his past experience as a police officer, working with dogs trained to detect drugs and explosives through their sense of smell, and wondered if these animals could also be used to detect the presence of Xylella.
Di Noia and his team found that a group of California experts had perfected how to use dogs' sense of smell to detect bacteria on citrus fruits (I'll link the search here). Encouraged by the possibility, he discussed the idea with theNational body of Italian dog lovers (ENCI) and with CNR experts. The Xylella Detection Dogs were born.
How do dogs work against Xylella?
From a purely "mechanical" point of view, a dog's nose captures odors much the same as a human's, but it has some unique characteristics that make it truly extraordinary. In fact, during inhalation and exhalation, the receptors present in the dog's nose detect the molecules in the air and send information to the brain. The front of the nose serves to humidify incoming air, aiding the sense of smell, and the air is then pumped into the lungs and receptor-rich olfactory chamber.
This is where the most incredible difference is noticed: dogs have 20 times more olfactory receptors than humans. When the dog exhales, the air comes out of two lateral fissures of the nose and not directly from the nostrils: this allows a constant and continuous sniff, and the capture of large quantities of odours. Dogs hear so many more than we do. How many? So many, to the point that we can be considered "blind" to smells compared to them.
Having secured this gift, however, it is necessary to make it bear fruit. And this depends on the goodness of the training. Serena Donnini, expert ENCI dog trainer and coordinator of the Xylella Detection Dogs experimental program, believes that some dog breeds such as the springer spaniel, the German shepherd, the cocker spaniel and the labrador are the best for this task. In any case, even among them it is necessary to select those with the best personality, the most playful and greedy.
What you don't do for an award
To train a dog to recognize the smell of an infected plant, it's important to develop a reward system. According to Donnini, the more a dog loves an object or a toy, the more likely he is to look for it. Trainers start by hiding a hollow rubber toy inside, to get the dog to work on its search skills. The choice of material is due to its particular smell, which dogs particularly recognize. Every time the dog finds the game, he gets a food reward.
Over time, the rubber is gradually removed from the object to increase the dog's concentration. Next, the trainers introduce the "target" scent into the game. Gradually, the dog learns to signal when it recognizes the target odor by receiving a reward. CNR scientists play a key role in supplying Xylella-infected plants for training dogs. The team of Donato Boscia, plant virologist and head of the unit responsible for studying Xylella, is currently perfecting the study of the molecules released by infected plants and better perceived by dogs.
A precious help against Xylella
Xylella is difficult to control as some infected plants show no visible symptoms. For this reason, dogs could be a valuable aid in stopping the spread in key places such as greenhouses and ports, real crucial hubs for this parasite. In fact, it is believed that Xylella arrived in Puglia through a coffee plant imported from Latin America.
Sniffer dogs could be deployed to inspect plants and locate infected ones, halting the advance of Xylella and giving time for the olive oil industry to rebuild its invaluable heritage, or for science to build a "electronic nose" capable of doing the same job.