LEARNING ON THE FLY
Citizens are helping scientists discover more about the invasive spotted lanternfly.
When the invasive spotted lanternfly was discovered in Berks County, scientists knew little about its behavior. It had no natural predators to keep its numbers balanced. Researchers weren’t even sure what it liked to eat, except for the Ailanthus altissima, known as tree of heaven, another invasive already here.
But since the fateful invasion seven years ago, scientists are learning more about the spotted lanternfly, which has spread to at least 34 Pennsylvania counties and to surrounding states. Recent research indicates that chickens and other birds eat the bug, while the pest itself is attracted to tall silhouettes.
Yum, spotted lanternfly
Last year, researchers at Penn State sought help from citizens to observe whether birds would eat the spotted lanternfly. They received 660 photos and observations submitted to scientists in the College of Agricultural Sciences. Chickens and praying mantises were ahead in the race to eat the spotted lanternfly, according to Anne Johnson, a doctoral candidate in entomology. She is conducting the study with Kelli Hoover, professor of entomology.
The hope is that finding predators in our environment would be a great biological control option and useful in guiding management practices, according to Kelli Hoover, professor of entomology in Penn State’s College of Agricultural Sciences.
“The overwhelming response to our request demonstrates what we suspected — that native predators may play a larger role in spotted lanternfly control than may have been assumed previously, perhaps giving us more biological options to help manage this pest,” she said.
However, Johnson cautioned in a news release that while the results of this study look promising, more research is needed to substantiate the impacts native predators will have on lanternfly populations.
In spotted lanternfly’s native environment of Asia, several predators, including parasitic wasps, devour it. However, importing new species to the U.S. as a control
measure requires numerous studies on environmental impact and regulatory approval, which is a lengthy process.
Leading the bird predators is the chicken, with cardinals, catbirds, blue jays and the tufted titmouse rounding out the top five. In the arthropod category, the praying mantis takes the top spot as the most reported predator; yellow jackets, orbweaver spiders, wheelbugs and ants also were strong contenders.
There were a few surprises among the reports, including sightings of squirrels, bats, frogs, goldfish and a garter snakes ingesting lanternflies.
“Being that these species also are predators, it makes sense,” Hoover said.
The past year’s research focused on predation of the adult stage of spotted lanternflies; currently, the scientists are gathering data on predation of eggs and nymphs.
Other aspects of the research will focus on whether the spotted lanternfly’s preferred diet — Ailanthus altissima, known as tree of heaven — influences how it might taste to birds. The researchers theorize that the chemicals in tree of heaven might cause the insect to have a bitter flavor, especially in later life stages when the pest is eating profusely and has gained the characteristic warning colors of red and black.
“From what we have observed so far and from studies on responses of birds to suet containing spotted lanternfly fed on tree of heaven or reared on other host plants, it appears that storage of bitter tasting toxins from tree of heaven is indeed somewhat of a deterrent to predators, unless they learn how to avoid these toxins, which apparently
they can do by avoiding eating the wings,” Hoover said.
There also is the potential that eating spotted lanternflies, particularly those that have fed on tree of heaven, could be toxic to predators. While the citizens’ observations currently do not support this notion, with many reporting no difference in behavior following predators’ lanternfly consumption, Johnson and Hoover plan to delve further into the theory.
The researchers anticipate having a report ready for publication this fall. Their preliminary findings, which Johnson presented at the Eastern Branch of the Entomological Society of America’s meeting last month, could help homeowners this season.
Johnson suggests homeowners take steps to attract these predators.
Pole attraction
The spotted lanternfly’s attraction to vertical silhouettes could help monitor and trap it, recent research shows. It’s a behavior that has been observed and capitalized on in a relatively new circle trap control.
Research from the laboratory of Tom Baker and entomologists in Penn State’s College of Agricultural Sciences, recently published in the Journal of Insect Behavior, shows spotted lanternflies are visually drawn toward and seemingly captivated by vertical objects such as utility poles, a behavior that could be valuable in predicting where the pests might be heading.
Baker’s research is laying the foundation for future strategies to monitor and possibly trap the invasive planthopper.
These findings show that telephone
poles attract flight-dispersing spotted lanternflies, which are visually drawn to turn and land on the poles when they are less than about 10 feet away. They remain on the pole for many minutes, even hours, while crawling up toward the top to try to take flight again.
However, a large proportion of those launching themselves from the pole are drawn back to the pole, which serves as a sort of “visual magnet” from which the insects cannot escape for a while. The pole thus attracts and retains a large proportion of the lanternflies that are drawn to it.
“The spotted lanternfly feeds on more than 70 plant species, making it a great concern to U.S. tree-fruit and grape growers, as well as to the forest products industry,” said Baker, distinguished professor of entomology and chemical ecology, in a news release. “Understanding the how and why of its flight capabilities and its attraction to stimuli from the environment can help us better exploit these behaviors to assess, and possibly thwart, future threats from this pest.”
This latest study is an offshoot of experiments on the insect’s flight behaviors and dispersal patterns led by Baker and his colleagues Andrew Myrick, assistant research professor of entomology, and Michael Wolfin, postdoctoral research associate.
Their flight-dispersal research efforts began during late summer and early fall in September and October of 2017 and 2018 at a fruit farm near Oley and at Dorney Park in Allentown. Both locations had been severely affected by spotted lanternfly infestations.
Baker’s team had found that, in the lanternflies’ apparent quest to find new sources of food to complete their development and then mate, they will fly onto and crawl to the top of the nearest vertical surfaces — including inanimate objects such as buildings and telephone poles and host and nonhost plants — and launch themselves into the wind.
Because lanternflies cannot generate much lift, only thrust, their normal flight paths conform to gradually descending, straightline trajectories in which they are able to traverse usually only 30 to 150 feet over the ground before landing.
Baker reported that their landing sites are indiscriminate with respect to species of trees, bushes and inanimate objects.
“The lanternflies’ forced landings on the ground due to insufficient lift are indiscriminate, too,” he said.
An exception to the typical low-to-the-ground flights occurs on days with high temperatures and rising air currents, allowing the low-flying lanternflies to be lifted to higher altitudes, with the now high-flying adults being transported downwind for perhaps thousands of yards.
It is on such occasional latesummer days during the past few years when huge swarms have been deposited by the tens of thousands — much to the alarm of the human population — in shopping center parking lots, gas stations and industrial and residential areas within heavily infested regions, Baker pointed out.
However, he said that the pest’s typical, low-to-ground flight coupled with its visual attraction to tall vertical objects may provide an effective and inexpensive way to monitor and even trap the insect.
“Telephone poles, which are plentiful and visible from the roadway, could be used by field scouts to document the presence or absence of spotted lanternfly by driving along and examining the poles at designated intervals,” said Baker, who also suggested the possible use of poles as “attractand-kill stations” to protect designated areas.
Despite the importance of these natural flight-dispersal abilities, a method of travel for the lanternflies that citizens should be very concerned about is human transport of adults and egg masses via trains, trucks and recreational vehicles, Baker noted.
“People who are traveling through or residing in an area affected by spotted lanternfly should check their vehicles and items they are transporting before leaving to ensure they are not carrying these unwanted hitchhikers to new locations,” he said.