An invasive species is devastating Pennsylvania's fledgling wine industry and spreading into neighboring states, leaving behind dead vines and sticky gunk. The next big vineyard threat to winegrowing regions throughout the U.S.? The spotted lanternfly, aka SLF or Lycorma delicatula.
The SLF is not really a fly. It's more of a hopper that leaps from destination to destination. It's big for a bug: 1 inch long and 2 inches wide with its wings extended. It travels in packs like locusts, moving through a vineyard or orchard, devastating the plants, then moving along to the next fertile ground.
It doesn't eat vines. It sucks the lifeblood out of them, using its proboscis to reach the sweet sap inside, drinking its contents and leaving behind sticky waste, euphemistically referred to as "honeydew," which coats the plant, disrupting photosynthesis and attracting mold. While the insect does not feed on fruit clusters, one winemaker described wine made from grapes on an infested vine as having a "cabbagey" odor.
Native to southern China, the SLF was identified in a backyard in Berks County, Penn., in 2014 and since then has spread through 14 Pennsylvania counties. Isolated infestations have been found in Virginia, New Jersey, Delaware and Maryland. There have been sightings in New York and Massachusetts as well. The USDA and state departments of agriculture have posted alerts in nearly all states with wine regions.
Calvin Beekman, owner of Beekman Orchards near Reading, Penn., raises peaches, apples, nectarines and grapes on his family farm. He discovered evidence of the pest in 2014. In 2017, his vines bore no fruit and now all 40 acres are dead. "There is no economic reason for me to even go forward with grapes," he said. "We've got to individually dig each plant out now."
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Richard Blair, owner of Setter Ridge Vineyards in Pennsylvania's Lehigh Valley, says that after killing off his vineyard, the population of bugs seems to have moved on. "We first found them in our vineyard in 2014. We didn't know what they were," he said. "In 2015 we knew what they were, but we didn't know what to do. In 2016, there were millions and they devastated the vineyard. And now they're just gone. They apparently exhausted the food source and moved on."
The insect is known as a "good hitchhiker" as it will lay eggs and attach itself to any smooth, flat surface, such as trucks, railroad cars and containers, as well as to any of its 70 host plants and trees. But vines are a particular favorite.
"So far, the SLF seems to be moving at a rate of about 10 miles per year," said Heather Leach, a spotted lanternfly extension associate at Penn State University. "There have been sightings in the Finger Lakes District but no infestations detected as yet."
Parasitic Wasps and Mind-Controlling Fungus?
As with most invasive pests, the first line of defense seems to be to throw anything at it that might work. Several pesticides are known to be effective on the SLF. But Gino Razzi, owner of Penns Woods Winery in Chadds Ford, Penn., said, "You spray your vineyard and three days later, they are back. Right now, we have to spray every seven days." The challenge with spraying any pesticide is making sure no traces are left on or in the fruit at the time of harvest. Then there's the cost.
Multiple efforts are instead looking to natural predators that might target the SLF. While the threat is confined to the East Coast so far, California is already working on one possible solution. In 1998, when the glassy winged sharpshooter was detected in California's Temecula Valley, growers were scrambling to knock out what appeared to be a serious threat to vineyard survival with no known effective treatments. It took some time before an effective collaboration between industry, the university and state agriculture officials coalesced, which still oversees fighting the pest today.
In an effort to avoid similar chaos with the SLF, Mark Hoddle, an entomologist and biological control specialist at the University of California Riverside, proposed a "Proactive Biological Control of the Spotted Lanternfly" project. He now heads the project, which was recently funded by the California Department of Food and Agriculture.
"We know it will eventually get to California," said Hoddle. "We're getting ready for it."
The project involves testing two parasitoid wasps native to China that are known to attack both the eggs and nymphs of the spotted lanternfly. They cannot be released directly into California until scientists know whether the parasitoids will also attack several native species of lanternflies. They're being tested simultaneously in labs in California and by the USDA in New Jersey.
Two Cornell University professors have found another potential predator: two species of fungal pathogens that kill the SLF. One in particular, Batkoa major, has been called a zombie fungus. Once its spores infect a lanternfly, it somehow compels the host to climb up its host plant. Once the bug gets high enough, fungal fibers kill it and spores burst out of the insect's body, raining down on other lanternflies below.
