Of Tree of Heaven and Lanternflies

Of Trees of Heaven and Lanternflies

Photo image courtesy of Penn State Extension. 2021.

If you’re reading this, chances are you’ve heard about the Spotted lanternfly. Since they arrived in Allegheny County last year, it’s possible you’ve seen them already. If you haven’t, you’ll likely see them within the next few years.

Spotted lanternflies, which are not flies but actually leaf hoppers, have voracious appetites. Nymphs and adults suck the sap from many plant species, taking away the sugars they make for themselves via photosynthesis. To make matters worse, their high metabolism means they excrete a lot of waste. Their sugar-rich excrement falls on the foliage of the plants they’re feeding on which invites black sooty mold to grow, reducing the plant’s photosynthesizing capabilities.

Though they seldom kill plants, they often cause stress which makes plants – notably trees – more susceptible to disease. Spotted lanternflies lay copious amounts of eggs in fall which hatch in late spring.

Nuisance vs. Invasive

A spotted lanternfly laying eggs on a tree downtown.

Spotted lanternfly, often abbreviated SLF, is more than a pest; it’s capital “I” invasive. Species become invasive when they are taken out of their native range and are able to exploit the new terrain when natural predators don’t recognize them as a food source.

The word “invasive” is a specific term. While tent caterpillars and bag worms are often considered garden pests, they are native to eastern North America and play a part in Pennsylvanian ecosystems; as such, they’re not invasive. Even fall armyworm, which has been receiving a lot of attention lately, is not invasive. Fall armyworms are the larvae of an eastern North American moth and while their ability to damage lawns is a nuisance, many birds eat them on their migration south and keep their numbers from reaching ecologically destructive levels.

Aggressive vs. Invasive

Plants such as Staghorn sumac (Rhus typhina.), American pokeberry (Phytolacca americana), and Canada Goldenrod (Solidago canadensis) tend to have aggressive growth habits but are not invasive as they’re also part of Pennsylvania’s ecosystems and have various pressures that also keep them in check. Japanese Knotweed and Amur Honeysuckle, native to east Asia, are invasive because they’re not recognized as a food source by herbivores in any meaningful way, and are able to spread rampantly. Their spread displaces native plants.

Knowing that the word “invasive” is a distinct term helps us recognize the threat various species pose, like Spotted lanternfly.

It’s presumed that part of what makes SLF unappetizing to predators are the sour compounds they ingest from their favorite tree – Tree of Heaven – which is an invasive tree that was brought over to North America as an ornamental a century ago. If SLF were host-specific and only fed on Tree of Heaven (Ailanthus altissima), we’d have a biocontrol for Tree of Heaven. Unfortunately, they’re “generalists” and will feed on many plants, especially woody species. If you have a Tree of Heaven on your property, remove it as soon as you can. Tree of Heaven behaves as a beacon to SLF and help proliferate their spread.

Tree of Heaven Identification

Be careful as several native trees resemble Tree of Heaven, such as Staghorn Sumac (Rhus typhina), Smooth Sumac (Rhus glabra), and Black Walnut (Juglans nigra). We don’t want to to cut down the wrong trees. These species share similarities, notably compound leaves (many leaflets held on central “stem”) but the differences are noticeable with a closer look. Leaf identification is important because sumacs and juvenile black walnuts can be similar in growth habit to Tree of Heaven.

Leaflets on Tree of Heaven are smooth with a little “bump” at each base. When crushed, leaves emit a sour, pungent odor. Compound leaves are often, but not always, longer than sumacs.

Leaflets on Staghorn and Smooth sumac are serrated, like a saw edge. They emit no odor when crushed. Stems of staghorn sumac are fuzzy while stems of smooth sumac are smooth.

Leaflets of Black Walnut are less visibly serrated. Walnuts usually lack the red and orange fall tones of sumac and Tree of Heaven, and often appear more tattered by late summer or early fall.

Compound leaves have many leaflets. Tree of Heaven (left), Black Walnut (center), Staghorn Sumac (right). Note that leaf size can vary based on environmental conditions so pay more attention to leaf shape and scent.

 

 

 

 

 

 

 

 

 

 

 

 

Managing Spotted Lanternfly – Swat and Inspect

Photo image courtesy of Penn State Extension. 2021. The white glue-like covering is fresh which becomes mud-colored with time.

If you see SLF on the ground, step on them. The best way to do it is to come at them head-on as they are incapable of flying backwards. If they do happen to fly away, try again. SLF are leaf hoppers and after several attempts to fly away, will tire out. A flyswatter works well too. It makes a difference because every 2 lanternflies you kill, you eliminate 30-50 offspring the following year.

You should also inspect your landscape for SLF egg masses in fall, winter, and early spring. Females prefer to lay their eggs on smooth surfaces, usually on trees and branches where the bark isn’t furrowed. They also lay eggs on smooth inanimate objects such as houses, sheds, vehicles, and stone. Fortunately, they’re easy to identify and can be rendered nonviable by scraping them into rubbing alcohol. Be careful to not confuse SLF egg masses with the egg casing of the Carolina Praying mantis; to date, mantids seem to be the only insect willing to eat SLF.

Managing Spotted Lanternfly – Traps

An old egg casing of the Carolina Praying mantis on a nursery tree. 

You can also manage SLF with specially made traps that target nymphs and their natural urge to climb upward. Don’t use exposed sticky traps as they catch many beneficial insects, birds and bats unless you tailor them to avoid collateral damage. You can also use traps modeled after pecan weevil traps.

For more information: https://extension.psu.edu/how-to-create-a-wildlife-barrier-for-a-spotted-lanternfly-sticky-band-trap and https://extension.psu.edu/how-to-build-a-new-style-spotted-lanternfly-circle-trap

A volunteer Staghorn sumac at the nursery: a great tree for fall color and stabilizing hillsides.

Avoid insecticides as many beneficial insects may suffer from their use. Keep in mind that fireflies, for example, spend one or to two years in the soil as larvae and are sensitive to pesticides. That said, if you think your use of an insecticide is justified, here’s a resource from Penn State Extension you should follow: https://extension.psu.edu/spotted-lanternfly-management-and-pesticide-safety

More information on SLF management: https://extension.psu.edu/spotted-lanternfly-management-resources

Pennsylvania has taken the lead on SLF management so you can find a lot more information though Penn State Extension here. https://extension.psu.edu/spotted-lanternfly

If you have SLF on your property, don’t focus on eradicating them as it’s rarely feasible to eradicate invasive species. Instead, you want to focus on managing their populations. The best thing you can do right now is take preventative measures to reduce their populations on your property and, more importantly, their spread. As such, make sure none are hitchhiking in or on your vehicle when you travel. Mitigating their proliferation as much as possible buys scientists time to research and trial effective control methods.

My advice to you is to be educated, vigilant, and when you do see SLF, do something about it.

Here is a great video to share with everyone you know: https://www.youtube.com/watch?v=3KwglQ3Inn4