Scientists Train Dogs to Sniff Out Invasive Spotted Lanternfly Eggs Before They Hatch

The spotted lanternfly, a colorful but devastating invasive insect from China, has spread across the eastern United States, damaging grapevines, fruit trees, and hardwoods at an estimated cost of $500 million annually. The insect lays its egg masses on any flat surface—tree bark, fence posts, cars, lawn furniture, even the undersides of RVs—and the eggs are nearly invisible to human eyes. But not to a beagle's nose.

A pioneering partnership between the Pennsylvania Department of Agriculture and the nonprofit Rescue Beagles Network has trained seven formerly abandoned beagles to detect spotted lanternfly egg masses by scent, then paw at the location so a human handler can scrape off and destroy the eggs. The program, called LanternWatch K9, has already prevented an estimated 2.3 million egg masses from hatching in its first year of full deployment.

"Beagles have about 300 million scent receptors in their noses," said Dr. Margaret Chen, the program's lead trainer. "Humans have 5 million. When we walk through a forest, we see trees and leaves. A beagle smells the tree's species, the age of the leaves, the fungus on the bark, the footprint of a squirrel from three hours ago, and—if we have trained them correctly—the faint waxy odor of a lanternfly egg mass covered in mud and moss."

The training process is classic positive reinforcement, adapted from drug and bomb detection dogs. Chen starts with a plastic tube containing a single lanternfly egg mass (collected and sterilized so it cannot hatch). The beagle learns that sitting next to the tube earns a treat. Then the tube is hidden in increasingly complex environments: under leaves, inside a hollow log, behind loose bark. Finally, the beagle works on real egg masses in the field, alerting by freezing and pointing their nose at the exact spot, then scratching gently with one paw.

"The paw scratch is our signal," Chen said. "If the beagle scratches, we know the eggs are within a two-inch radius. We scrape the area with a putty knife, collect the eggs in a bag, and destroy them by freezing or burning. The beagle gets a toy—a tennis ball or a squeaky pig—and we move to the next tree."

The beagles themselves seem to love the work. LanternWatch K9 dogs are all rescues who were surrendered because they were "too high energy" or "too destructive" as household pets. One of the program's stars, a three-year-old beagle named Gumbo, was returned to a shelter twice for chewing through drywall. On the job, Gumbo works four hours a day, covers eight to ten miles of forest, and finds an average of 215 egg masses per shift. He sleeps soundly in his crate afterward, too tired to chew anything.

"These dogs were not bad dogs," Chen said. "They were bored dogs. Beagles were bred to hunt in packs for hours. They need a job. Lanternfly detection is the perfect job. It uses their nose, their stamina, their persistence, and their desire to please. A beagle with a job is a happy beagle. A beagle without a job eats your couch."

The program's success has attracted international interest. Australia, which has not yet detected spotted lanternflies but fears their arrival, sent a delegation to Pennsylvania to study the beagle program. New Zealand, which has a similar biosecurity program using beagles to detect invasive ants at ports, is now adapting the lanternfly training for its own dogs. Even California, where the lanternfly has not yet established a population, has contracted LanternWatch K9 to train a team of four beagles for early detection at border inspection stations.

Local farmers are enthusiastic. "Before the beagles, we were spraying pesticides blind," said Miriam Sacks, owner of Sacks Vineyard in Lehigh Valley, which lost 40% of its crop to lanternflies in 2022. "We would spray the whole vineyard every two weeks, hoping to hit the nymphs before they grew wings. It cost a fortune and it killed beneficial insects too. Now we bring Gumbo through twice a season. He finds the egg masses, we scrape them, and we spray only the infested trees. Our chemical use is down 80%. Our grape yield is up 30%. And Gumbo gets all the belly rubs he can handle."

Critics have raised concerns about the dogs' safety: lanternflies are not toxic, but the pesticides used to kill them are. Chen emphasized that the beagles never work in areas that have been recently sprayed. "We schedule the dogs before the first spray of spring and after the last spray of fall," she said. "If we have to spray during the summer, we keep the dogs out of that zone for the required re-entry interval. No dog has ever shown signs of pesticide exposure."

The program is not cheap. Each beagle costs $15,000 to train, plus $5,000 annually for veterinary care, handlers' salaries, and equipment. But compared to the cost of uncontrolled lanternfly infestations—which can exceed $1,000 per acre in lost crop value and chemical control—the beagles are a bargain. Pennsylvania has already expanded LanternWatch K9 from 7 dogs to 22, with plans to deploy them statewide by 2028.

For Gumbo, the expansion means more work, which means more tennis balls. When asked whether Gumbo understands the ecological importance of his mission, Chen laughed. "Absolutely not," she said. "He thinks he is playing a game called 'find the smelly thing, get the squeaky pig.' That is fine. That is the secret of working dogs. They do not need to save the world. They just need to enjoy their job. Saving the world is a side effect of a good walk with a good human."