Spotted lanternflies damaged more than a quarter of Pennsylvania’s vineyards last year, and the persistent pest isn’t showing any sign of retreat this year.
Heather Leach, a spotted lanternfly expert with Penn State Extension, talked about detection and management during a June 17 webinar.
In 2019, 80% of grape growers reported using management techniques for spotted lanternfly, and 30% reported damage, including yield losses and vine death.
Leach warned growers that 2020 might show higher numbers.
“2020 we expect to be an extremely problematic year,” she said. “I have never seen populations this high of spotted lanternfly.”
Because the spotted lanternfly is an invasive species that only recently became a problem in the U.S., there isn’t any baseline data on how to manage it.
“We’re still learning a lot more about spotted lanternfly — practically every day,” Leach said.
Though the spotted lanternfly feeds on more than 70 plants, the grape is one of its favorites.
Still, tree species growing nearby — like black walnut, maple, birch, willow and sumac — could be attracting more of them to vineyards.
Leach encouraged growers to think about the surrounding landscape when planning spotted lanternfly management.
In a study of eight vineyards, Leach found that a higher density of spotted lanternfly is found toward the edge of the crop area.
“What we’re seeing is that 67% of your total spotted lanternfly population is within the first 60 feet of your block,” she said.
Now that researchers have a better idea of where the pests will be within a vineyard, Leach suggests scouting regularly and knowing where the hot spots are.
Research suggests spraying insecticides when vines have about 15-20 nymphs per vine and then spraying again when vines have 5-10 adults per vine.
Spotted lanternflies are currently in the nymph stage, typically found feeding on the shoots of the vine. After they reach adulthood, they tend to feed on the trunks.
Leach said that at this point in the life cycle, growers could probably scout for hot spots and utilize spot spraying. This could help keep the population down later in the season.
Damage to grapevines will come from all life stages. Infestations reduce photosynthesis, transpiration, brix values and cold hardiness.
Leach noted that the honeydew excreted by the lanternflies, which promotes the growth of sooty mold, has not been seen on fruit clusters. So, the marketability of the grapes is not one of her concerns.
Spotted lanternflies reach their population height in vineyards in September and October, during the adult stage.
The research also shows that it takes about 31 days from the first adult lanternfly spotting until peak range. While within the peak, the greatest flight activity is typically in the afternoon.
Last year, one vineyard recorded 350-450 spotted lanternflies per vine during peak season, Leach said.
Insecticides are currently the best management option. Other strategies include removing tree of heaven, an invasive host tree, as well as removing egg masses in winter months. But Leach doesn’t think these two options are significantly effective.
“I am not convinced that (removing egg masses) is going to reduce your population of adults,” she said, explaining that many of the adult lanternflies come into the vineyard from outside.
Leach also warned that insecticides will kill beneficial pests, so growers need to watch out for secondary pest flare-ups, such as mites, mealybugs and leafhoppers.
In addition to insecticides, there is a fungal pathogen, Beauveria bassiana, that will attack spotted lanternfly. This fungus is already on the market and is being studied by Leach and other researchers.
One study found that applying the fungus in July reduced the nymph population by 46%.
Leach recently started a new study of the fungi at Blue Marsh Lake, just outside of Reading, Pennsylvania, an area with a large lanternfly population.
“It’s something that we’re very excited about,” Leach said, adding that the fungus does not harm humans and also won’t cause any harm to the groundwater.
Other ongoing studies include using exclusion netting, insecticidal netting, and using tree of heaven as a trap tree.
“We’re still learning,” Leach said. “We’re trying to do our best to understand this insect.”