Surviving Spotted Lanternfly

This immature spotted lanternfly nymph was photographed in the Boyertown area of Berks County, Pennsylvania. Photo by Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org.

Pennsylvania winegrape producers take it on the chin

By Stephen Kloosterman, Associate Editor, Fruit Growers News

This article originally appeared in the January 2019 issue of Fruit Growers News. Reprinted with permission and updates to quotes for timeliness.

The Mid-Atlantic and Midwest are better known for apple production than wine, but it is winegrape growers who perhaps have the most to lose from the latest pest threatening that region.

Spotted lanternfly (SLF) is in Pennsylvania and is likely to spread to New York and Michigan, extension agents say.

“We are hoping to delay this as much as possible with the current control program in place in Pennsylvania, New Jersey, and Virginia,” said Heather Leach, an extension associate with the Pennsylvania State University (PSU) Department of Entomology. “Detections of adult SLF have been found in Connecticut, Delaware, Maryland, and New York (currently, no population is verified in these states). This highlights that SLF is a good hitchhiker and spread is likely.”

New York State and Michigan are susceptible to SLF infestations.

“Based on modeling, we expect if it does hit these regions, it will likely be able to establish in them,” Leach said.

Pest Profile

SLF is an invasive planthopper that feeds on hardwood trees and hops as well as fruit trees, ornamentals, and grapevines. Host plants may ooze sap and wilt, may show leaf curling, and may even die.

“Grapevines are being hit hard by SLF, and this is the crop where we are seeing a significant economic loss,” Leach said. “After heavy populations of SLF, growers have experienced vines that could not survive the winter or vines that survived but did not produce fruit in the following year. Up to 100-percent yield loss and subsequent vine death have been observed in grapevine.”

She added that while SLF also feeds on apples, peaches, and other tree fruit, they’ve done this for only a few weeks in mid-late September before moving on to other hosts.

Pennsylvania has a growing local wine scene with more than 200 wineries that produce more than one million gallons of wine a year, according to the Pennsylvania Winery Association. Grape growers in the region are concerned about SLF.

Leach recently conducted a survey of growers in the region.

“We found that most of the grape growers were already aware of this pest and the threat it poses, but they are not knowledgeable on how to control it,” she said. “This, of course, is understandable, as we are still learning about how to control it ourselves! The priorities from these growers were to develop insecticide recommendations, develop biological control methods, and determine the impact of SLF on long-term vine health. These are key issues we plan to be addressing in our future research.”

Field Intel

An adult spotted lanternfly specimen. Photo by Pennsylvania Department of Agriculture, Bugwood.org.

There are already, however, a few recommendations for discouraging the bugs. Julianna Wilson, a tree fruit integrator for Michigan State University’s Department of Entomology, recently spoke about the bugs at the Great Lakes Fruit, Vegetable, and Farm Market EXPO in Grand Rapids, Michigan. She offered a few basic tips:

• Stop the spread of SLF by keeping an eye out for adults, nymphs, and egg masses. Report sightings to extension agents or your state’s appropriate department. See neipmc.org/go/slfqri for detailed state-by-state information.
• Scrape egg masses off tree trunks and other flat surfaces where they are laid—this will kill the eggs.
• Band some trees to catch nymphs and monitor the population level.
• Remove invasive tree of heaven, a.k.a. Chinese sumac or stinking sumac, as this is SLF’s favorite host.
• Apply insecticides.

In 2018 and 2019, PSU conducted insecticide efficacy trials for adult SLF on potted grapevines. Five products were found to have killed more than 50 percent of SLF up to seven days after application, and two products, Actara and Brigade, were effective up to 14 days after application.

“To be honest, SLF is really easy to kill compared to most other insect pests in these systems,” Leach said. “We’re finding that they’re susceptible to most classes of insecticides, including action with some organic products (i.e., neem oil, insecticidal soaps).”

“However, the problem is that SLF are feeding on so many things in the surrounding landscape that even after a grower treats their orchard/vineyard, they re-infest the trees/vines within a few days. SLF peak populations also coincide with harvest or just before harvest, limiting the options available to growers (to be compliant with preharvest intervals). This has been our biggest struggle, and we are currently evaluating several different spray programs to determine the best sequence and products to be used.”

Other Strategies

Some encouraging discoveries have been that SLF seems to be susceptible to many of the same things that gypsy moths are.

“We have identified two different fungal pathogens that attack SLF in the field,” Leach said. “One of these is closely related to the gypsy moth fungal pathogen, but it is not the same one. These appear promising, but we still need lots of lab and field research to understand if these are potential products to be used. Testing on Beauveria products against SLF is in its preliminary stage, but this appears promising as a control measure. Ann Hajek out of Cornell (University) is partnering with David Biddinger and Nina Jenkins at Penn State for this research.”

Spotted lanternflies congregate in large groups as seen on the trunk of this cherry tree. Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org.

Generalist predators such as praying mantis are not thought to have much effect on SLF individually. Leach said there are several parasitoids identified in China that attack SLF.

“These are parasitoids not known to occur in the U.S., so they are currently held in a quarantine lab to undergo studies on SLF and other closely related insects,” she said. “Importing these species could be a very promising tactic to reduce SLF populations, but requires lots of money and time to test for potential negative effects.”

For growers who don’t yet have SLF, Leach recommends scouting the farm (especially the wood edge) for tree of heaven.

“If you have it, either consider removing it, or use it as a monitoring tool to watch for SLF,” she said. “Other plants that appear to be preferred by SLF include grapes (wild and cultivated), maple (silver and red, mostly), river birch, willow, and others.”