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News & Views September 2018 Issue

Dogs Can Smell Disease in Trees, Save Crops

Belgian malinois

A Belgian malinois named Cobra sits amidst a grove of avocado trees that she checked for disease. Female dogs tend to be better at this job than males, says Florida International University researcher DeEtta Mills, PhD. Males like to make themselves busy marking vertical objects — like tree trunks.

You've probably heard that with their keen sense of smell, dogs can sniff cancer on their owners and even be trained to warn of a hypoglycemic attack in someone with diabetes because of changes in the odor of the person’s breath. Now, researchers are learning that dogs can also protect our food supply — in a big way.

Investigators at Florida International University made the finding when they trained dogs to detect disease in avocado trees. Avocados are the second largest tree crop in Florida after citrus fruits, and they are becoming more and more popular in the U.S. We ate more than 2 billion pounds of them in 2017, up from just 680 million pounds in 2003.

But in South Florida, where the most American avocados are grown after California, avocado trees have been dying at an alarming rate from a disease known as laurel wilt. Signs include brown, dried leaves that cling to the tree for as long as 12 months. This is followed by stem and limb dieback and, eventually, decline in other parts of the tree that causes it to die. The disease was brought into this country by red bay ambrosia beetles that hail from Asia. They were inadvertently introduced into the U.S. in untreated wooden packing material.

Once the signs of disease start appearing, it is generally too late to save the tree. Enter the dogs. Researchers trained three of them (one Belgian malinois and two Dutch shepherds) to detect laurel wilt by scent, teaching them to sit once they discovered a sick tree. During the course of the study, 229 “trials” were performed. Only 12 yielded a false result — even in harsh weather conditions like high heat and humidity that can affect a dog’s olfactory performance.

California and Mexico are watching closely, as their avocado industries are much larger than Florida’s. But the results look extremely promising, showing that dogs work not only to protect us but also our food supply — and our very economy.

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