An Invasive Pest: Spotted Lanternfly

Recently, I made a quick Facebook post about the Spotted Lanternfly. It received a lot of views and shares, but many people still have quite a few questions about them, so I figured I would write a blog post to provide additional information.

The Spotted Lanternfly (Lycorma delicatula) is an invasive pest in the United States. It is native to Asia and is thought to have arrived from China to Pennsylvania - first discovered in Berks County, PA, in 2014. Though originally found in Southeastern PA, as of May 2020, it has been reported as spotted in 26 PA counties (Allegheny, Beaver, Berks, Blair, Bucks, Carbon, Chester, Columbia, Cumberland, Dauphin, Delaware, Huntingdon, Juniata, Lancaster, Lebanon, Lehigh, Luzerne, Mifflin, Monroe, Montgomery, Northampton, Northumberland, Perry, Philadelphia, Schuylkill, and York). However, it is likely to be more widespread than that. The PA Department of Agriculture relies on reports by individuals throughout the state for their data. 

In a research paper put out by Penn State (which can be found here) the annual economic impact to Pennsylvania agriculture could be as high as $99.1 million statewide.

A Spotted Lanternfly (SLF) generation lasts for 1 year. The eggs are laid in the fall - primarily on tree bark, but others have reported finding masses on decks, outdoor equipment, rocks, or siding as well. Really any solid surface outdoors will do. The egg masses look like dried mud. 

Egg Mass (Photo Credit: E. Swackhamer)

Each egg mass can have 30 to 50 eggs. The eggs hatch in spring. Many report seeing their first nymph stage in late May/early June. I believe this year, the very first report in PA was from late April. They start out small (about 1/8 to 1/2 inch) in length and are black with white spots. Two days ago, I saw three in my garden beds (2 on a David Austin "Young Lycidas" [AUSvibrant, 2008] rose and 1 on a peony). If I wasn't carefully deadheading the roses, I wouldn't have noticed as they were truly very small. At this stage, they do not yet fly but are good jumpers. 

The first three nymphal stages of SLF are black with white spots. The fourth nymphal stage before reaching their adult stage is red with white dots and black stripes. 

SLF adults are found in July and are active through the summer and fall. This is the stage most people are familiar with - they're about an inch long with black bodies and brightly colored wings. At this stage they can both jump and fly. Their wings typically remained closed unless in use.

Early nymph stage - about 1/8" (found late April through July) (Photo Credit: PA Dept of Agriculture)

Late stage nymph - about 1/2" (found July through September) (Photo Credit: PA Dept of Agriculture)

Adult, Wings Closed - about 1" (Found July through early December) (Photo Credit: PA Dept of Agriculture)

Adult, Wings Open (Photo Credit: PA Dept of Agriculture)

SLF was primarily thought to go after certain fruit-bearing trees, vines, tree-of-heaven, and certain tree saplings. At this point, they're known to infest at least 65 different plant species.

Last year, I personally noticed (and reported to the Penn State Extension) that their early nymph stage was very attracted to my roses as well as the new growth on our trumpet vines (which we have since removed - more on that can be read in our other blog posts). This year, I am seeing widespread reports of SLF nymphs infesting roses, peonies, and hydrangeas, from LVRS members; as well as members in various gardening groups across the state. 

New data suggests that roses, grapevines, and tree-of-heaven seem to be their primary food source when the eggs hatch (and will be most destructive for these plants in May and June). Once they are in their adult stage, then their focus shifts to trees such as black walnut, butternut, river birch, willow, sumac, silver maple, red maple, etc. 

On roses, the nymphs pierce into the new growth with their mouth and feed like they're using a straw. They excrete a substance called "honeydew" which is a sugar-rich waste product. This encourages the growth of black spot on roses. Last year, even with weekly preventative treatments for black spot, I still had to resort to heavily pruning my roses several times throughout the year. Once in their adult stage, they left my roses alone and I was able to enjoy some blooms in late July through October. 

On other plants, the damage is similar. The honeydew acts as a substrate for sooty mold and various fungi that thrive in sugary environments. Left untreated, this acts as a major plant stressor. This leaves the plant overall less healthy and its even more susceptible to other stressors (diseases, weather, additional pests). It can be responsible for canopy dieback on trees or cause death for flowers, tree saplings, and vines.

Because of how mobile these pests are, there is no way to PREVENT them from moving onto your property and measures need to be continuously taken to keep them controlled. 

So you may be asking yourself: "What do I do to get rid of these monsters?!" There are several steps we can all take to try and slow their spread. The first step starts from September through May: 

Egg Scraping - Walk around your property and check for egg masses (pictured above). Remember, they are not just on trees - look on the side of your house, on your deck, your shed, cement blocks, outdoor equipment, rocks, etc. Take a plastic card (like your LVRS membership card? 😉) or a putty knife works really well too. Scrape them into a bag/bottle/container filled with rubbing alcohol (or all that stockpiled hand sanitizer 😅). They can also be smashed. Remember, every mass has between 30 - 50 potential SLF's in them that will go on to destroy plants and have their own egg masses. Every single mass you destroy DOES make a difference even if it doesn't feel like it.

(Photo Credit: PA Dept of Agriculture)

Tree banding - now these have been controversial because left "as is" they can injure and even kill birds, bats, etc. HOWEVER, they can be safely used with some minor modifications. These sticky bands can be found from local garden centers or ordered online - simply use some pushpins to secure them in place. Please see the picture below:

(Photo Credit: Heather Leach)

The tree band is a sticky band that is wrapped around the trunk of a tree. Originally, these were not covered and birds and bats were getting stuck. However, if you cover the band in chicken wire, it is still effective for catching SLF but it prevents other animals from getting stuck.

Another type of tree trap is a funnel-style trap (mesh wrapped around the tree leading to a container to trap SLF). Some companies produce these traps commercially or you can make your own. This style of trap is pictured below:

(Photo Credit: Unknown)

Insecticides - Contact insecticides to control nymph and adult SLF:

N = nontoxic; S = slightly toxic; M = moderately toxic; H = highly toxic; — = data not available.
¹Some products allowed for organic production.
²There are many products containing essential oils which vary widely for efficacy against SLF. The two products tested against SLF were “SLF Killer 2" and “Purely Green."

Insecticides - Systemic insecticides to provide longer periods of control on adult SLF:

N = nontoxic; S = slightly toxic; M = moderately toxic; H = highly toxic; — = data not available.

Note: The listing of any products in these tables is NOT an endorsement OR specific recommendation of any products. Other products with the same active ingredient should also work in the same way, but they may have different rates or formulations. For use in Pennsylvania, be sure the product is registered for the site and purpose of use (e.g., vegetable garden versus ornamental trees). These tables are based on the experiments Penn State Extension has done to date and should not be considered final or complete.

Disclaimers on Insecticides from the Penn State Extension:

Water Contamination
Every precaution should be taken to protect surface water and groundwater from pesticide contamination. Trunk injections pose the smallest risk to contaminating water because the insecticide goes directly into the tree. Soil drench applications should only occur directly adjacent to the trunk of the tree, as directed on the label. Soil drenches should not be applied to sandy soils or where the water table is shallow. Both dinotefuran and imidacloprid can persist in groundwater for extended periods. When exposed to sun, both of these compounds break down readily. To protect surface water, systemic insecticides should not be applied near open water sources (ponds, lakes, streams).

Pollinators and Other Insects
Many of the trees on which SLF have been observed feeding in high densities are also pollinated by bees (e.g., maples and oaks). It is possible that trees treated with systemic insecticides could have insecticide residue in the flowers and nectar the following spring. Neonicotinoid insecticides, in particular, have been associated with bee health decline. Additionally, there are many native insects that utilize these trees at the same time as SLF (e.g., caterpillars, beetles, lady beetles, lace-wings, parasitoid wasps) and could be affected by the treatment. Pyrethroids can also be damaging to beneficial insect populations and could cause populations of secondary pests, such as mites and scale, to increase. Generally, systemic insecticides are considered to have a reduced impact on beneficial insects compared to broad-spectrum foliar-applied insecticides. We are currently conducting research to determine the effect of SLF treatments on pollinators and other non-targets.

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If you see SLF, please report sightings here. 

Data in this post was pulled from the Pennsylvania Department of Agriculture, the Penn State Extension, and the United States Department of Agriculture.

The blog post "Featured Image" is of Lorraine Phillips removing Spotted Lanternfly nymphs from her roses. (Photo Credit: Jessica Griffin). It was taken from an article written by Maria Panaritis of "The Philadelphia Inquirer." The article can be found here.