The invasive pest spotted lanternfly (Lycorma delicatula) likely arrived in the United States as an egg mass hitchhiking on building stone imported from Asia to Southeastern Pennsylvania. The pest was discovered in 2014 when a forester observed adult lanternflies massing on the trunks of tree-of-heaven close to building stone company’s lot. Tree-of-heaven is itself an invasive import from Asia, notorious for its extreme adaptability to urban environments and known to invasive species managers as being very difficult to control. Biologists don’t yet fully understand the relationship between tree-of-heaven and spotted lanternfly, but there is considerable overlap in their native ranges and co-evolution seems likely. What is known is that spotted lanternfly shows a strong preference for tree-of-heaven in the late juvenile to early adult stage of their annual life cycle, which is illustrated in the below graphic, adapted from Penn State Extension. In late summer into early fall, lanternflies will cluster on tree-of-heaven trunks and engage in a feeding frenzy, which is either fascinating or gross, depending on how you feel about large numbers of rather large insects.
We wouldn’t care too much about any of this if spotted lanternfly only damaged tree-of-heaven. The problem is that during its early nymph stages, it is much less choosy and will feed on a number of woody species including grape vines (wild and cultivated), apple trees, stone fruit trees, and a variety of native forest trees. Spotted lanternfly feeds on the sap of woody plants, and in the process of feeding, they excrete a sweet, sticky substance called honeydew. Honeydew promotes aggressive growth of mold, which further injures attacked plants, shortening their lives and reducing fruit production. One Pennsylvania grape grower reported a 90% decrease in harvest from impacted vines. Another challenge is that although the adults frequently lay eggs on tree-of-heaven trunks, they can and do lay eggs on other outdoor surfaces, such as brick or stone, patio furniture, shed walls, playground equipment, sides of stationary vehicles, etc. To make things more even more difficult, the unhatched egg masses, which persist in place from the time they are laid in the fall until hatching in spring, are flat and beige, camouflaging well on most outdoor surfaces.
Spotted lanternfly has gained ground in the Eastern U.S. in the five years since its discovery as shown on this map produced by the New York State Integrated Pest Management Program.
Spotted lanternfly has not reached the Midwest yet. Of the Midwestern states, it is probably of greatest concern to Michigan and Ohio, both due to proximity to the infested states and due to the cost of potential impacts. In addition to being known for its forests, Michigan is among the top states nationally for the production of grapes, cherries, apples and nursery plants, all of which can be devastated by spotted lanternfly. These resources are all in play in Ohio as well, though on a smaller scale.
So, now the million dollar question: Can Michigan, Ohio and other Midwestern states reduce the risk of spotted lanternfly invasion by managing tree-of-heaven? It isn’t a fail-safe solution, but it certainly wouldn’t hurt. It would be overstating the current understanding of the relationship to say that spotted lanternfly absolutely requires tree-of-heaven to complete its life cycle, but abundance of the tree certainly seems to facilitate its reproduction and spread. EDDMapS and MISIN data indicate that tree-of-heaven is widespread in the Lower Peninsula of Michigan and Ohio, so spotted lanternfly could find these areas hospitable.
Earlier this year, Pennsylvania took a key step in combating tree-of-heaven by placing it on the state’s noxious weed list, effectively banning its sale and directing state resources towards control. In the Midwest, Indiana, Minnesota, Ohio and Wisconsin have also banned sales of this species. Although this species hasn’t been stocked by reputable garden centers or nurseries for decades due to its invasiveness and other liabilities that make it a poor choice for landscaping, seeds and live plants are still available through e-commerce sites like Etsy and eBay.
The best approach to combating spotted lanternfly is likely multi-faceted. It will combine tree-of-heaven control with quarantines (both internal quarantines put in place by the infested states and additional quarantines by concerned potential recipient states), public education to improve the likelihood of early detection, and continued research on methods to control the insect pest if it does arrive.
Suggested reading to learn more:
- Lansing State Journal on risk posed to Michigan
- Penn State Extension on the relationship between spotted lanternfly and tree-of-heaven
- USDA’s spotted lanternfly pest alert
By Clair Ryan, Midwest Invasive Plant Network Coordinator, August 2019, updated June 2020
