Keeping tabs on the spotted lanternfly

For those living in Pennsylvania and the Mid-Atlantic region, the spotted lanternfly (Lycorma delicatula) must carefully be tracked and monitored. The spotted lanternfly is an invasive species from China that first arrived in Berks County, Pennsylvania, in September 2014. Ever since its arrival, the spotted lanternfly population has steadily increased. The spotted lanternfly is a planthopper and prefers to feed on the tree of heaven (Ailanthus altissima). It also feeds on 70 other species of plants, including ornamental and hardwood trees, many that are important to the nursery trade.

According to the Penn State Extension spotted lanternfly resource page, the insect excretes honeydew (a sugary substance), which attracts insects such as bees and wasps. This buildup also promotes the growth for sooty mold, a fungi that can severely damage and weaken affected plants.

Economists at Penn State say the spotted lanternfly could cost Pennsylvania’s economy $324 million in damages, as many of the trees the insect feeds on are of high economic importance. And while the species is a planthopper, it still has the ability to travel long distances by attaching itself or its egg masses onto materials or automobiles.

Nursery Management charted the rise of the spotted lanternfly in our January 2019 issue (which readers can view here: bit.ly/SLFJan2019), and it’s time to revisit how much progress experts have made when it comes to controlling the pest. The Pennsylvania Department of Agriculture (PDA) and researchers at Penn State Extension are doing their best to contain the insect and learn more about it to keep it from spreading.

Quarantine

The PDA has created a map charting the spread within the state, which can be found at bit.ly/PDASLFMap. As of March 2020, the PDA has expanded the quarantine zone. The map is color-coded to show areas of infestation, with existing quarantines marked as yellow, counties added in 2020 as light blue and infested areas in the counties added in 2020 as dark blue.

“I will say, my caveat there, is that those counties aren't completely infested — they're considered partially infested,” says Heather Leach, extension associate in the entomology department at Penn State.

Shannon Powers, press secretary for the PDA, also notes the bump in quarantined counties from 14 to 26.

“We previously had 14 quarantined counties in primarily Southeast and South-Central Pennsylvania. And those were counties where there was sort of a widespread established insect population, but very late in the season, we've done a lot of outreach all over the state and we've had reports of isolated insect populations,” says Powers.

The Pennsylvania quarantine affects vehicles, plants, wood and stone products, and outdoor household items.

Nursery growers, as well as all agricultural and non-agricultural businesses working within the quarantine, that move products, vehicles or other conveyances within or out of the quarantine are required to obtain a spotted lanternfly permit. Businesses located in spotted lanternfly infested areas of other states must also have a permit if traveling or transporting goods into Pennsylvania. To learn more about the permitting process, visit bit.ly/SLF_PA_permit.

“The map is very telling,” Powers says. “When you look at the map, you can really see this insect doesn't fly across three counties to get to a new place. It's absolutely traveling with people.”

Containment procedures

Powers stresses that containment, treeing specific areas and communication with the public is key to avoiding further spread. Collaboration is also necessary. The PDA, the U.S. Department of Agriculture (USDA) and Penn State Extension are working together to fight the insect. Penn State Extension does the research and educational outreach, while the USDA and the PDA do the control work.

“The strategy has been largely to remove the tree of heaven, the female tree of heaven, which is the preferred host for the insect. They prefer to feed on it and breed there and live there, and in doing so we leave a specific male tree,” Powers says. “And we treat that male tree with a systemic insecticide and also band the trees so that the systemic insecticide, the insects that are missed by the sticky band wrapped around the tree, feed on the tree and then die.”

Leach, who works closely with the PDA, says it uses a systemic insecticide called dinotefuran.

“This one is probably one of the best insecticides that we have available,” says Leach. “That active ingredient in particular has been the best performer for us in terms of residual activity and being reliable there.”

The tree of heaven is also an invasive species from China. Its removal is difficult because it grows in clumps and sends out shoots nearby to where it is planted. This makes for an easy and abundant launchpad for any incoming spotted lanternflies.

“We've used herbicide on the trees to kill them and physically remove the trees, although they're quite a challenge to remove. It's been a little bit of a perfect storm of an invasive species combination,” Powers says.

New research

Leach says they have a list of insecticides which controllers know are effective against the spotted lanternfly, but they are digging deeper to understand the predictability of the spotted lanternfly.

Early in the season, the insect prefers hosts like black walnut, rose bushes and tree of heaven. However, later in the season, researchers really start to see the problem when it comes to ornamental plants — both in nursery and urban settings — with movement onto maples, styrax, willows and other important nursery crops.

“We can kind of predict when that's going to come, and then when you should be putting on those control measures, so that's great. We're still at a point where we don't have very many options for management. That's where a lot of our research is focused right now, is trying to understand how we can disrupt that movement or disrupt some part of their behavior so that the growers, the operations have better success and better efficacy when they do control measures,” Leach says.

Matthew R. Helmus, a biodiversity and ecology assistant professor at Temple University, is looking at modeling for the spotted lanternfly to better understand higher risk pathways, where is it likely to spread and how fast it could happen.

“Then we also start to see spread towards the Chicago region, including Ohio, and Southwest Michigan. Part of the reason we start to see the Chicago area lighting up is because we have so much transportation and trade with that area, and lots of rail lines connecting that,” Leach says. “We expect to see spread towards that area, but then the model even picks up spread on the West Coast and even spread in the South. Based on some climate models, we do expect a lot of lanternfly to spread throughout a large part of the United States and even in the southern regions of Canada.”

Leach is optimistic in Penn State’s research efforts and says they recently gained funding for a four-year, $7.3 million specialty crop research initiative grant from the USDA. The grant was awarded to 10 institutions, including Penn State, Cornell, Rutgers and Virginia Tech.

“It's really bringing together this team of experts to focus on our specialty crops,” Leach says.