Wednesday, August 05, 2020

Spotted Lanternfly in Princeton


Most people by now have heard of the spotted lanternfly, an insect native to China, Vietnam and parts of India that somehow showed up in eastern Pennsylvania in 2014. A leaf hopper with distinctive markings and colorful wings, it spread rapidly as it sucked the juices out of grape vines, orchards, and trees like Ailanthus, black walnut, maple and red oak.


Two years ago, local papers reported a sighting of spotted lanternfly in northeastern Princeton. Last year, the summer of 2019, a couple friends reported seeing it in Princeton--Mimi found a few in her backyard in western Princeton; Scott saw some in Herrontown Woods near the parking lot. 


For me, it didn't become real until I encountered this curiously tilted nymph on a butternut tree leaf near Veblen House in Herrontown Woods in early July. A Penn State Extension post describes the insect's colorful development from egg to nymph to the winged adults that emerge in late July.

For some reason, I had avoided writing about the spotted lanternfly. Maybe I was maxed out on the world's problems, and didn't really want to delve into the prospect of yet another introduced insect wreaking environmental havoc. 


Unlike the Emerald ash borer, which has gone largely unseen as it quietly kills every untreated ash tree in Princeton, 

the spotted lanternfly sounded poised to make a highly visible and messy invasion. The PA Dept. of Agriculture published a pdf with graphic photos showing mildewed foliage and tree trunks covered with the adult insects. And because plant juice is very dilute, the sucking insects need to move a lot of juice through their bodies to get the nutrition they need. That means that both nymphs and adults produce large amounts of "honeydew", which drops down from the trees and vines, and coats foliage on the ground with sugary liquid, promoting the growth of mold. Their egg cases look like mud, affixed to trees or cars or most anything. It sounded like our habitat restorations and garden beautifications would be reduced to a tattered, moldy mess.

Below are compiled some research and experiences with spotted lanternfly this past weekend at Herrontown Woods. 

Ailanthus--the Spotted Lanternfly's favorite food

Turns out that the spotted lanternfly has a strong preference for sucking the juices of Tree of Heaven (Ailanthus altissima). Native to China, Ailanthus is fairly common in Princeton and can be invasive, forming clones and sprouting aggressively from its roots if cut down. A stand of Ailanthus can be used for trapping the spotted lanternfly. Penn State extension offers tips for homeowners on this. 


At the Herrontown Woods botanical garden, next to the parking lot, we have an Ailanthus growing, and sure enough, some adult lanternflies were found clinging to its bark.


Looking up, the Ailanthus leaves appear to be getting eaten, though the lanternflies are said only to suck from the trunk and the stems, not the thinner tissue of the leaves themselves. 

In a sense, the preference for Ailanthus is good news. An invasive tree is being attacked by a newly introduced insect from a similar region of the world. But the tree is also helping the insect expand its numbers through the summer, and toxic compounds in Ailanthus, when ingested by the lanternfly, may confer some protection from predators.


The lanternfly's honeydew is causing sooty mold to grow on the plants underneath the tree.  The NJ Dept. of Agriculture info sheet reports that the sap dripping from "weeping wounds" on tree trunks can attract stinging insects. 

Probably the best thing to do is to take down the Ailanthus, using techniques described here.

More advice for homeowners

There's an enjoyable and clever article on various tactics on the MercerMe site. For instance, the adults are very quick to jump if you try to squash them. The article says their reflexes slow down with persistent efforts, however. Will test that next time. Another thorough read for homeowners is at this link, including a test to see if chickens would eat them. They didn't, but more research is needed.

Longterm prognosis

Will the spotted lanternfly prove to be a longterm calamity, like the Emerald ash borer, or fade into the background as a passing problem? Will it be a lasting plague for vineyards and apple orchards? An article reports that few lanternflies were seen this year in the area of Pennsylvania where it was first discovered five years prior.  Local Princeton arborist Bob Wells is quoted in the Town Topics as saying that though vineyards and apple growers have reason for concern, for homeowners the insect "won't be much of a threat at all." I inquired on a listserve that includes land managers in Pennsylvania who have had the insect around for several years now, and got mixed responses. One observed reduced numbers one year, then a rebound the next. 


It can be hard to know if you have spotted lanternfly in your trees. My friend LisaB, who lives near Herrontown Woods, had a couple black oaks fall near her property in late July, and was surprised to find numerous SLF nymphs on the leaves that until then had been elevated 70 feet above the ground. She had seen none in her yard up to that point. Her photos show the last nymph stage (red), 

  
and a beautifully captured example of what a newly formed adult looks like. Documented in past posts on this blog, insects like cicadasbutterflies, and apparently spotted lanternflies as well, must hang down as they unfurl their new wings. If the wings brush up against any obstruction, they can easily become misshapened. 

Update, Aug. 6: Walking through Quarry Park, closer to downtown, I noticed some Ailanthus trees near Spruce Circle,  looked up at the leaves above, and saw them there as well, a few scattered adults sucking juice from the rachis of the compound leaves. Will the spotted lanternfly be background or foreground, a quiet addition or serious pest? Time will tell. 

In the meantime, it looks like removing Ailanthus trees would be the most straightforward way to limit this new arrival's numbers and impact.



Reporting: I tried reporting the Herrontown Woods and Quarry Park sightings. The email address bounced, and the telephone number is always busy. It may be that the state doesn't want to hear about sightings in counties where the insect is already present, or maybe it's so widespread by now that the information isn't helpful.


Does milkweed kill lanternflies?

On the leaves of common milkweed growing near our Ailanthus tree, I found several lanternflies belly up or immobilized, leading to speculation that the insects sucked juices from the milkweed and died from the toxins therein. 

Sunday, August 02, 2020

Lisa's Salamander Rescue


This spring in late April, I received a surprising email from my friend LisaB who lives out next to Autumn Hill Reservation, across from Herrontown Woods. An amphibian had mistaken the water sitting on top of her swimming pool cover for a vernal pool, and laid a cluster of eggs there. My somewhat informed guess? Spotted salamander eggs. 

What to do with this unexpected gift? The salamander was not completely off-track in having laid its eggs in a puddle suspended over a swimming pool. Through uncanny luck, the swimming pool's owner happens to care deeply about the amphibians that inhabit the woods behind her house.

Lisa had contacted me back in March--March 15 to be exact--to report that the frogs in the neighborhood had been on the move the night before. "This was definitely Herrontown frog migration night," she reported. "Dozens on the road at 5:30a, all headed" towards Herrontown Woods to mate and lay eggs. "I only saw them in a relatively narrow band of ~a half mile, from the entry to Autumn Hill to the curve at Stone Hill Church. They were mostly moving in the dark early this morning--by 7am they were gone. Hope that protects them to some extent. Traffic picks up after 7." She suggested we organize next spring to serve as crossing guards for amphibians needing to cross Herrontown Road to get to their mating grounds, as is done elsewhere in the state.

On May 25, Lisa sent me a report on what she had decided to do with the salamander eggs, which otherwise would have been lost when the maintenance crew came to service the swimming pool. Since it's inappropriate to remove salamander eggs from a nature preserve, Lisa took this backyard gift as a rare opportunity to see salamander development up close.


"I put some in a deep vernal pool in Herrontown Woods and hung on to a few. They live outside in a tank so they get all the usual temperature variations, plus bonus mosquito larvae to eat. They seem to really like live blackworms, which I am now growing in my fridge (uh, don't tell my kid). I'd love to see one develop spots, which takes a few weeks after transformation. They already have puny little front legs!"

On June 24, another update:
"Salamander larvae are starting to transform! Losing their gills and showing their spots. Voracious carnivores!"

And on July 7, more detailed reports begin about the salamanders' metamorphosis, mixing affection with the close observation honed in her career as a scientist: "The two that transformed first flew the coop. For now I put lids on the tanks, so the next three to transform are still here. Some cool things I didn't know:"


1) "As they start to transform, their GILLS start to develop bright yellow spots just before they regress."


2) "Each one has a unique spot pattern that coalesces and intensifies as they transform, which makes them easy to tell apart. Not sure what nucleates the spots."



"This sequence of photos, taken two days apart, shows the development of spots on a transformed salamander."

"They become very shy once they transform. The larvae are just hanging out in the water column. I know they're about to transform when I look in the tank and I can't find them. The ones that have transformed are always burrowed under the moss. Interesting, for a stage with what looks like aposematic coloring ("don't eat me! I'm brightly colored and probably toxic!"). Probably they aren't actually toxic, and so the bright yellow spots pretty strongly select against anyone who is ever out in the open."

3) "The darkness of the larval stage seems influenced by substrate--ones raised on light rocks are lighter in color than ones raised in a pile of leaf litter. Not sure if it's a developmental camouflage or they're just dark because they're eating/covered in leaf gunk. "

"Man, do they eat a lot of blackworms! 1/8 lb so far."



Here are spots developing on a "new guy." Photos taken on days 1,2,3, 6, and 7.

By mid-July, thoughts turned to what to do with the salamanders once they've grown. "Technically I think I'm not supposed to release them, given there is some risk of introducing new pathogens into the local population (e.g., from the worms I feed them, which came from afar). Two did escape, though, so that ship may have sailed."

The Watershed Institute didn't have room. Salamanders apparently, and fortunately, given the potential danger to wild populations posed by poaching, don't make very good pets. They prefer to remain hidden, and can live up to 20 years. Many have toxins in their skin, and can easily absorb harmful oils and chemicals on our skin if we touch them. 

Finally, Lisa reached out to the Mercer County wildlife center, which then reached out to the senior biologist from the New Jersey Division of Fish and Wildlife Endangered and Nongame Species Program, who gave the following advice:

"From what I’ve read below I consider this to be a pretty low risk release and would recommend her to release them as near as she can to reasonable habitat by her property and best case would be to release them during the late morning when there’s some rain or release them an hour or so after sunset during a rain." 

One thing I've learned while putting this post together is that spotted salamanders (Ambystoma maculatum) have a longer incubation period than most species. Most vernal pools dry up once the trees leaf out. Only a few stay wet enough long enough to sustain the larvae until they metamorphose into juveniles.

Lisa sent a link describing how spotted salamander eggs incorporate algae into the body of the embryo. They become solar salamanders. The algae symbiotically provides energy and eats the salamander's waste. The algae fades away during the larval stage of the salamander.
Thanks to LisaB for all these photos and information. One more thing she shared speaks to why this was such a meaningful experience for her:
"I've been turning over stones looking for salamanders since I was a kid, and have seen hundreds of Eastern Redbacks. Once, when I was <10, one of the other kids found what I now know was probably a spotted salamander, and came running to tell the others (we thought they were lying about a salamander the size of a hotdog). That was the closest I've come to seeing one, despite the fact that they are all over here, until 40+ years later one decided to lay eggs on our pool cover."



Saturday, August 01, 2020

Mile-a-Minute Vine in Princeton



Each year I conduct a solo campaign to keep the highly invasive weed Mile-a-Minute out of Princeton. It's a prickly annual vine that grows each year from berries produced the year before. Knock it out before it produces berries, and eventually there will be no berries to sprout. Otherwise, the infestation will grow and birds will spread the berries across all of Princeton, to spring up in backyards and vex homeowners with its thorns and rampant growth.

I know of two infestations--one at the Princeton Battlefield, the other down off West Drive on the gravel road to Rogers Refuge. Yesterday, passing by Princeton Battlefield, I stopped to uproot what Mile-a-Minute I could find and leave it on the lawn to dry in the sun. Like most annual plants, it has whimpy roots and can easily be pulled, wearing a good pair of gloves.



Princeton Battlefield has a remarkable history, which makes it all the more remarkable how ahistoric the landscaping is. Non-native turf is surrounded by giant kudzu-like topiaries of non-native porcelainberry vine growing over the native dogwoods that were proudly planted for the 1976 bicentennial. There's little hint of what the Clark Farm looked like on that fateful day in January of 1777. The lack of botanical context doesn't fit with the people and era the Battlefield is meant to celebrate. Plants were important to George Washington and other leaders of his time. They were farmers. It's not coincidence that the United States Botanic Garden was built to stand next to the U.S. Capitol building. What grew upon the land mattered back then. They didn't mow the lawn and think their work done.

Seeing a landscape so invaded and out of balance, I sometimes imagine a hospital with no doctors or nurses, only custodians dedicated to keeping the place clean. The patients are on their own, unless a volunteer doctor happens by to treat some localized infection. That's the situation in the vast majority of our landscapes, cared for by custodians armed with raucous mowers and leaf blowers, oblivious to the complexities of nature and its needs. 

In the meantime, I pull the Mile-a-Minute, trim back some small portion of the porcelainberry vines so the dogwoods might live another year, and wonder at the world's disconnect with nature.

The two photos show 1) porcelainberry vines overwhelming a dogwood tree, and 2) another sea of porcelainberry in which only the similarly invasive Canada thistle can manage to lift its pink flowers above the swarm.