First encountered in the United States in Pennsylvania in 2014, the spotted lanternfly (Lycorma delicatula) had spread to New York, Delaware, and Virginia by early 2018. The invasive insect threatens Tree of Heaven as well as grapes, hops, and fruit trees, and it has a penchant for hitchhiking. Anyone sighting spotted lanternfly is urged to report it to their state agriculture department or local extension office. (Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org)

By Meredith Swett Walker

Meredith Swett Walker

In the summer of 2014, in Berks County, Pennsylvania, a keen-eyed state Game Commission officer spotted an unusual insect congregating in an ailanthus tree. It was a large plant hopper, about an inch long, with distinctive spots and red hind wings. The officer followed his training and called it in. “He gave us a chance,” says Sven-Erik Spichiger, entomology program manager for the Pennsylvania Department of Agriculture.

It was a spotted lanternfly (Lycorma delicatula), a sap-sucking insect native to Asia. Just more than a month after this first report, Pennsylvania issued a quarantine in select counties in an attempt to restrict the spotted lanternfly’s movement. “From our perspective, this pest is quite frankly terrible,” says Spichiger.

In the summer of 2017, Spichiger visited a property where one or two spotted lanternflies had been seen, but the owner had recently reported there was no real infestation. That situation had changed rapidly. “I deal with all kinds of invasive pests throughout the state—that’s my job—and I have to be honest I was awestruck when I visited the site. I haven’t seen anything quite like that before. The only thing I can liken this to is a massive mayfly hatch off the river. It’s that uncomfortable to be standing around,” says Spichiger. “This pest has such a tremendous potential to breed and increase its population size that it can overwhelm individual properties and entire communities almost overnight.”

If Spichiger sounds alarmed, it’s because there is a lot at stake. The spotted lanternfly may have a preferred host—Tree of Heaven (Ailanthus altissima)—but it will also feed more than 70 other plant species, including grapes, hops, and fruit trees. According to the Pennsylvania Department of Agriculture: “This pest poses a significant threat to the state’s more than $28 million grape, $87 million apple, and more than $19 million peach industries, as well as the hardwood industry in Pennsylvania, which accounts for nearly $17 billion in sales.”

The U.S. Department of Agriculture agrees. In February 2018, it announced it was committing $17.5 million in emergency funding to stop the spread of the spotted lanternfly in southeastern Pennsylvania. This was after spotted lanternflies were reported in New York and Delaware in the fall of 2017 as well as Virginia in January of 2018. The new funding will allow the USDA’s Animal and Plant Health Inspection Service (APHIS), in cooperation with the Pennsylvania Department of Agriculture, to expand surveillance and control programs in an effort to stop the spread of spotted lanternfly and reduce its population in the core infested areas in Pennsylvania.

These adult spotted lanternflies (Lycorma delicatula) were filmed on grapes in the summer of 2017. At around the 13-second mark, one of the insects in the upper left can be seen repeatedly excreting a stream of honeydew. The large amounts of honeydew secreted by spotted lanternflies leads to growth of sooty mold, which can severely damage the host plant. (Video via Erica Smyers, Penn State Entomology Department)

Like other leafhoppers, the lanternfly feeds on plant sap, which damages the plant, but greater harm comes as a result of the honeydew that the insect excretes in abundance. This sweet, sticky fluid promotes the growth of sooty mold, which is extremely damaging to fruit crops. Thankfully, effective control measures exist for the spotted lanternfly, but most alarming about the pest is its potential as a hitchhiker.

Adult lanternflies can fly, but it may be the least mobile of their life history stages—their egg masses—that has the greatest potential for long-distance travel. Spotted lanternfly egg masses are inconspicuous, and females will lay them on virtually any surface: trees, lumber, yard furniture, vehicles. Combine that with the fact that their preferred host plant, ailanthus, is an invasive itself that tends to grow in disturbed areas such as around parking lots or along highways and railroad tracks. Ailanthus is already growing in 44 states. Female Spotted lanternflies that are ready to lay eggs tend to be lazy, dropping onto the nearest convenient surface and depositing roughly 30 to 50 eggs.

Spichiger envisions a coal car stopped on an ailanthus-lined railroad track or an out-of-town pickup truck parked next to an ailanthus at a football stadium. A gravid female lanternfly drops down, deposits her eggs, and soon they are driven away to the next county or across the country.

Sooty mold, such as shown in this example at the base of a tree, results from a combination of sap flows caused by the spotted lanternfly (Lycorma delicatula) and honeydew excreted by the insect. (Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org)

The spotted lanternfly (Lycorma delicatula) passes through four nymphal instars. The first three instars are black with white spots (such as the one pictured at right). The fourth instar (left) develops red patterning on the head, thorax, and abdomen, while still retaining some white spotting. (Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org)

The spotted lanternfly (Lycorma delicatula) tends to aggregate in great numbers, such as shown on this backyard tree. Says one entomologist who tracks the pest: “This pest has such a tremendous potential to breed and increase its population size that it can overwhelm individual properties and entire communities almost overnight.” (Photo credit: Lawrence Barringer, Pennsylvania Department of Agriculture, Bugwood.org)

Egg masses of the spotted lanternfly (Lycorma delicatula) are very inconspicuous and may be laid on virtually any surface. (Photo credit: U.S. Department of Agriculture)

Tree of Heaven (Ailanthus altissima) is the preferred host plant for Spotted Lanternfly, but the insect will also feed on many other species of plants including, fruit trees, grapes and hops. (Public domain image)

Containing and eradicating the spotted lanternfly will require awareness, not just among the agriculture and entomology communities but also among homeowners, outdoorspeople, and others. The Pennsylvania Game Commission officer that called in the first report of this pest gave pest control authorities critical time to mobilize against the spotted lanternfly, and more keen eyes will be needed.

Spotted lanternflies are generally easy to identify. Spichiger stresses that, if you spot a spotted lanternfly or any other unusual insect, always report it to your state’s department of agriculture or your local county extension office.

Special thanks to Leigh Greenwood, outreach program manager, “Don’t Move Firewood” campaign, ‎The Nature Conservancy; Sven-Erik Spichiger, entomology program manager, Pennsylvania Department of Agriculture; and Julie Urban, Ph.D., senior research associate, Penn State Department of Entomology.

Meredith Swett Walker is a former avian endocrinologist who now studies the development and behavior of two juvenile humans in the high desert of western Colorado. When she is not handling her research subjects, she writes about science and nature. You can read her work on her blogs Pica Hudsonia and The Citizen Biologist or follow her on Twitter at @mswettwalker.

This video, taken in Pennsylvania in the summer of 2017 shows a swarm of spotted lanternflies (Lycorma delicatula) in an apple tree. The soft clattering sound is the insects hitting the leaves as they fly into the trees. (Video via Erica Smyers, Penn State Entomology Department)