What Are Spotted Lanternflies?

Adult Lanternfly with coloring and spots

Spotted Lanternflies (SLF) also known as Lycorma delicatula, are a "plant-hopper" type of insect that have taken over areas of the Eastern United States, especially Pennsylvania, and continues to spread unchecked by local ecosystems.  

SLF are native to certain areas of China, India, and Vietnam. In these areas, populations of Spotted Lanternflies are kept in check with natural SLF predators such as a type of wasp known Dryinus browni. Another type of parasitic wasp known as Anastatus orientalis has been observed to destroy a large number of Spotted Lanternfly eggs. 

Unfortunately, there are many areas outside these regions that do not have a species known to feed on Spotted Lanternflies. Without a natural predator, the lanternflies can grow and spread unchecked in an environment that doesn't know to consume it, thus becoming an invasive species. It has been found as an invasive species as far back as 2004 when SLF were discovered invading Korea. In three years time, the entire country of South Korea had evidence of Spotted Lanternfly infestations. Only a few years later it was found in Japan as an invasive species as well. 

How Did Spotted Lanternflies get to the US?

Berks County -- Ground Zero for the North American SLF infestation

It is postulated that Spotted Lanternflies made their way to the United States through a 2012 shipment of stone from China to a business in Berks County, Pennsylvania in the Philadelphia area that contained what is now
known to be SLF egg masses. In 2014, the first infestation was discovered in the same general area. 

The infestation was noted to be found on another invasive species, Ailanthus altissima, or the Tree of Heaven. Tree of Heaven is also native to China, and is invasive outside of China, especially in North America and Europe. Spotted Lanternflies preferentially inhabit the trunk and branches of the Tree of Heaven. Prompt removal of the trees has been crucial in maintaining SLF infestations, although Tree of Heaven is extremely difficult to rid of, and Lanternflies will happily infest other plants as well.    

Since 2014, the Spotted Lanternflies have spread to 45 out of 67 counties in Pennsylvania as of 2022. If not for an intensive quarantine and abatement program, it's likely this would've spread quicker and further. Pennsylvania, Ohio, Indiana, West Virginia, North Carolina, Virginia, Maryland, Delaware, New Jersey, Massachusetts, Connecticut, New York, and Rhode Island have reported infestations in 2022. 

Some researchers tracking the insect's movement and behavior believes that there is a small chance the Spotted Lanternfly reaches California by 2027. However, by 2033 it is almost likely that this will happen. 

Although adult lanternflies have wings, Spotted Lanternflies are mostly "plant-hoppers" and travel short distances through jumping. They are actually quite un-graceful, and adult flies are often seen flying into poles, walls, people, anything and falling to the ground.

Why are Spotted Lanternflies Bad? 

Spotted Lanternflies wreak havoc on the ecosystem. Since they have no current predators in the areas in which they are invasive species they can live, grow, and multiply freely without being killed by most other wildlife. The SLFs red coloring in their more mature stages acts as a ‘Hey don’t eat me, I could be poisonous’ signal to potential predators.

Spotted Lanternflies damage or destroy crops, vegetation, leafy plants, trees, vines, hops, and other plants. Damage is inflicted during feeding from their numerous bites which can pierce and suck on the plant to attain food. Feeding damage may cause dieback

Sooty Mold growing at the base of a Tree-of-Heaven

The flies typically do not feed directly on the fruit of a plant, but suck from the phloem (and stems,branches,trunks) of the plant. The phloem is similar to an artery of a human, as it is used to transport essentials throughout the plant, like sap. As they feed on sap and other sweet nectars from plants, they excrete honeydew. Honeydew is a somewhat sticky, sugar-laden liquid excreted as the lanternflies feed. In heavily infested area, such as a large tree, it is even possible to see the honeydew actively raining down from the higher branches.

Leaves of a Broccoli plant with Black Sooty Mold causing it to die

This honeydew, full of water and sugar, is the perfect combination for the development of black sooty mold, usually Cladosporium and Alternaria, but others may exist as well. On top of damage from the Lanternfly’s mouths themselves, the black sooty mold may prevent the plant from receiving proper sunlight and stunt its growth. Enough mold may result in the death of the plant altogether. Honeydew can also contaminate outdoor items, and build up on vehicle windshields which can be difficult to remove once set on the glass. All of this also reduces the quality of life for residents living in the affected infestation areas as well. 

Honeydew may also attract other bugs to the area and create additional nuisances. Ants, bees, and wasps are noticeably more numerous where Lanternfly honeydew tends to drop.  

A trifecta of Spotted Lanternflies, Yellowjacket Wasp, and Egg Mass (left) on a tree in late October. The wasp is attracted to the tree from the Lanternfly honeydew. 

 

Spotted Lanternflies also preferentially feed on the Tree-Of-Heaven, which produces toxic metabolites. These toxins don't affect the SLFs, but do affect others in the environment. These toxins help keep any potential predators away from the tree, and thus away from the lanternflies. Lanternflies will set up shop in many areas, though, if there are no Tree of Heaven growths anywhere, they seem to gravitate towards high sugar content plants, explaining their affinity towards grapes and why vineyards need to be especially vigilant. 

Spotted lanternflies can have a significant economic impact on agricultural industries, particularly those that rely on grape and fruit production. They can reduce crop yields and increase the cost of production, ultimately affecting the livelihoods of farmers and producers.

Spotted Lanternflies can also be a public health concern, as they have been known to swarm and cause traffic hazards, and can also pose a risk to people who are allergic to their saliva.

Here are some additional reasons why spotted lanternflies are considered to be bad:

• Spreading diseases: Spotted lanternflies are known to spread plant diseases such as grapevine leafroll disease and Pierce's disease, which can be devastating to crops and vineyards.
  
  
• Environmental damage: The spotted lanternfly can cause significant environmental damage by feeding on trees, which can lead to defoliation and weakening of the trees. This can also affect the habitat of wildlife and contribute to erosion and other environmental problems.
  
  
• Increased use of pesticides: The control of spotted lanternflies often involves the use of pesticides, which can have negative impacts on the environment and human health. The use of pesticides can also lead to the development of pesticide-resistant strains of insects, making control more difficult in the long-term.
  
  
• Increased costs: Controlling spotted lanternflies can be expensive, both for farmers and for the government. The cost of monitoring and controlling these pests can be substantial, and can ultimately impact consumers through higher prices for produce and other agricultural products.