Researchers at Washington State University (WSU) are working on a two-year project with specially trained dogs to detect the disease in cherry orchards. The study, funded by the Washington Tree Fruit Research Commission (WTFRC) and the Northwest Nursery Improvement Institute, showed that canines’ exceptional detection abilities could offer a promising alternative to current polymerase chain reaction (PCR) testing.
Why Use Dogs for Detection?
LCD is an incurable disease that causes small, unripe, and unmarketable cherries. Symptoms are typically visible only on the fruit during harvest. The rest of the year, the tree appears healthy, making early detection difficult.
Scott Harper, associate professor in the WSU Department of Plant Pathology, explained that dogs are faster and more sensitive than PCR tests. “Dogs are excellent at detecting low concentrations of the pathogen, which is difficult to do with PCR tests”, Harper said.
PCR tests are also expensive, and results are not immediate. “These tests are not commercially viable for many growers”, said Corina Serban, a WSU tree fruit extension educator. Additionally, because the disease occurs in small areas of the tree, PCR tests that rely on tissue samples can fail.
Training Aika and Humma
In May 2023, WSU researchers partnered with Jessica Kohntopp, an Idaho dog trainer who had previously taught canines to sniff out viruses in tomatoes, squash, citrus, and even COVID-19. For this study, Kohntopp trained Aika, a Belgian Malinois, and Humma, a Dutch Shepherd.
Using healthy and infected cherry trees, Kohntopp taught the dogs to alert by stopping next to the infected trees. infected plants. “For them, it’s a game, not a job”, Kohntopp explained. “They get very excited when they find the positive plants”.
Promising Results
The first tests were conducted in a greenhouse at the WSU Irrigated Agricultural Research and Extension Center in Prosser. The dogs successfully found the seven positive plants out of a group of nearly 200, also alerting them to one plant that later tested positive. In a subsequent blind study, in which Kohntopp did not know the plants’ status, Aika and Humma sniffed 1,380 plants with 101 positive results. None of the dogs had a false alarm, leading to a combined accuracy rate of 99.72%.
One of the most promising results occurred in a test involving five trees from a commercial orchard that had previously tested negative. Aika and Humma indicated otherwise. The researchers dug up the five trees and performed more rigorous PCR testing. The dogs were right: the PCR samples They confirmed that the trees were infected, demonstrating their ability to detect the disease at very low levels.
The ultimate goal is to make dogs like Aika and Humma accessible to commercial growers. Although the research is still ongoing, the results are very promising. The researchers plan to continue their work to study whether the dogs can detect the disease in nursery plants before they reach the orchard and how hibernating the trees affects detection.
“We want to scale this up to help the industry”, Serban said. “The biggest challenge is using science to test the dogs’ accuracy. Our research is still ongoing, but it’s very promising so far”.
