Of Trees of Heaven and Lanternflies

 

A spotted lanternfly I caught laying eggs on a tree downtown.

Photo image courtesy of Penn State Extension. 2021.

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

More than just a pest, spotted lanternfly is capital “I” invasive. Invasive species are not only inconvenient and annoying, they are highly and unnaturally destructive. Species become invasive when they are taken far out of their native range and natural predators don’t recognize them as a food source. This is in contrast with nuisance pests like most aphids which are by and large kept in check by natural predators. Even the fall armyworm, which has been receiving a lot of attention lately, is a nuisance but not an invasive. Fall armyworms are the larvae of an eastern North American moth and while their ability to damage a lawn is inconvenient, many birds eat them – especially on their migration south. They’re certainly aggressive but they are not invasive. Spotted lanternfly is on a whole ‘nother level.

Some plants are like this too. Some Sumacs (Rhus sp.), Virginia Creeper (Pathonesissus quinquefolia), and Canada Goldenrod (Solidago canadensis) are aggressive but are not invasive as this is their native range and they have various pressures that will keep them in check.  Japanese Knotweed and Amur Honeysuckle, on the other hand, are invasive.

Spotted lanternflies –  not flies nor moths but rather leaf hoppers – have voracious appetites. Nymphs and adults suck the sap from the phloem of many plant species (mostly woody plants), taking away the sugars they make for themselves via photosynthesis. To make matters worse, their high metabolisms means they excrete a lot of waste. Their sugar-rich excrement falls on the foliage of the plant they’re on and anything underneath which invites black sooty mold to grow which reduces the plant’s photosynthesizing capabilities. Though they die in winter, lanternflies lay copious amounts of eggs which guarantees next year’s life cycle. While some natural predators have been seen to peck at them, by and large, they are not viewed as appetizing.

Part of what makes Spotted lanternflies unappetizing are the sour compounds they ingest from their favorite tree – the Tree of Heaven – which is an invasive tree that was brought over as an ornamental a century ago. If they were host-specific and only fed on Tree of Heaven (Ailanthus altissima), that would be terrific as we’d have a biocontrol for Tree of Heaven. Unfortunately, they are “generalists” and will feed on many species of native woody plants. If you have a Tree of Heaven on your property, I suggest removing it immediately as they act like beacons to the lanternflies.

Be careful though as we have several native trees that look like of Tree of Heaven! They are Staghorn Sumac (Rhus typhina), Smooth Sumac (Rhus glabra), and Black Walnut (Juglans nigra). One thing we don’t want to do is to cut down beneficial trees! All of them have compound leaves comprised of many leaflets but the differences are noticeable.

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

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

Leaflets of Black Walnut are serrated too although its a lot finer than on sumacs. Walnuts don’t have red or orange tones in fall like sumacs and Tree of Heaven do and often appear more tattered.

Compound leaves of leaflets. Tree of Heaven (left), Black Walnut (center), Staghorn Sumac (right)

 

 

 

 

 

 

 

 

 

 

 

 

 

A volunteer Staghorn sumac at the nursery: a great tree to keep for fall color and stabilizing hillsides if you have the space.

How do we control lanternflies on our respective properties to reduce the risk of explosive populations? If you see them on the ground, you can certainly step on them. The best way to do that is to come at them from the front as they are incapable of flying backwards. A flyswatter works well too. For every 2 lanternflies you kill, you eliminate 30-50 offspring next year. You should also inspect your landscape for their egg masses. Females prefer to lay their eggs on smooth surfaces, usually on trees and branches where the bark isn’t too furrowed but they will also lay on inanimate objects as well: sheds, stone, house siding, cars, you name it. Matter of fact, egg masses laid on stone is how they ended up in the United States to begin with. Egg masses are easy to identify and should be scraped off into some rubbing alcohol. Be careful to not confuse their egg masses with the egg casing of the Carolina Praying Mantis – if there’s any insect that might adapt to eating spotted lanternfly en masse, it’ll be the mantids!

An old casing of the Carolina Praying Mantis. Notice how it’s more raised than Spotted lanternfly egg masses?

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

Probably the most effective control method is to catch the nymphs with specially made traps that prey on the natural urge of lanternfly nymphs to climb upwards. Don’t use exposed sticky traps as they catch many beneficial insects, birds and bats although you can tailor them to avoid that. You can also use traps modeled after pecan weevil traps! Go here 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

I would avoid insecticides as many native and beneficial insects may suffer from their use. If you do, use them conservatively and mindfully. Keep in mind the wonderful fireflies we have here spend one or even two years in the soil as larvae and are sensitive to pesticides that can leach into the soil. Here is a resourceful link on pesticides from Penn State Extension should you go that route. https://extension.psu.edu/spotted-lanternfly-management-and-pesticide-safety

To find more information on Spotted Lanternfly management: https://extension.psu.edu/spotted-lanternfly-management-resources

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

If you have them on your property, don’t obsess with eradicating them as it’s usually not feasible to totally eradicate invasive species. The best thing we can do is take preventative measures to reduce their spread and to keep their populations as low as we can so they do the least amount of damage possible. This will also buy scientists more time to develop controls that only target Spotted lanternfly. The best advice I can give is to be educated, be vigilant, and when you do see them, do something about it!

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