Dogs Smell Crop Disease Affecting Citrus Trees

    16 February 2020

    New research suggests that dogs might be able to help save diseased citrus trees.

    A group of scientists trained dogs to use their sense of smell to detect a crop disease called citrus greening. The disease has affected orange, lemon and grapefruit trees in the American states of Florida, California and Texas.

    The dogs can detect the disease weeks to years before it appears on tree leaves and roots, the researchers report. A study on their findings was published recently in the Proceedings of the National Academy of Sciences.

    In this April 2016 photo provided by the United States Department of Agriculture, detector canine
    In this April 2016 photo provided by the United States Department of Agriculture, detector canine "Bello" works in a citrus orchard in Texas, searching for citrus greening disease, a bacteria that is spread by a tiny insect that feeds on citrus trees. (Gavin Poole/USDA via AP)

    The report says using dogs is also faster, less costly and more exact than having people collect hundreds of leaves for lab analysis.

    Timothy Gottwald is a researcher with the U.S. Department of Agriculture and a co-writer of the study. He told The Associated Press, "This technology is thousands of years old – the dog's nose. We've just trained dogs to hunt new prey: the bacteria that causes a very damaging crop disease."

    Citrus greening is caused by a bacteria that is spread by a tiny insect that feeds on the leaves and stems of citrus trees. Once a tree is infected, there is no cure.

    The disease has also hurt citrus crops in Central and South America and Asia.

    In one experiment involving grapefruit trees in Texas, trained dogs were correct 95 percent of the time in telling the difference between newly infected trees and healthy ones.

    "The earlier you detect a disease, the better chance you have at stopping an epidemic" by removing infected trees, Gottwald said.

    Matteo Garbelotto studies plants at the University of California, Berkeley. He says the new research shows that dogs can detect an infection well before current methods. Garbelotto has been involved in similar research but had no part in the new study.

    Laura Sims is a plant scientist with Louisiana Tech University. She praised the steps taken to find out if the dogs were detecting the bacteria itself or a plant's reaction to an infection.

    To do that, the researchers infected different kinds of unrelated plants with the bacteria in a laboratory. The dogs were still able to pick out the infected plants.

    Gottwald said, "You've seen dogs working in airports, detecting drugs and explosives. Maybe soon you will see them working on more farms."

    I'm Jonathan Evans.

    Christina Larson reported this story for the Associated Press. Jonathan Evans adapted it for Learning English. Ashley Thompson was the editor.


    Words in This Story

    citrus – n. a juicy fruit such as an orange, grapefruit, or lemon that has a thick skin and that comes from a tree or shrub that grows in warm areas

    detect – v. to discover or notice the presence of something that is hidden or hard to see, hear, taste, etc.

    epidemic – n. an occurrence in which a disease spreads very quickly and affects a large number of people

    stem – n. the main stalk of a plant that develops buds and shoots and usually grows above ground