At this point, most people in agriculture know the impact that the invasive spotted lanternfly (SLF) can have. According to Dr. Julie Urban of the Penn State Entomology Department, SLF feeds on more than 70 species of plants and trees. Many of them flower and produce pollen – that sweet stuff that also sustains honeybees.
While the also-invasive Tree-of-Heaven is their preferred food choice, lanternflies are known as sapsuckers and have been affecting certain areas of ag harder than others. In addition to vineyards – which are very concerned – two other industries are reporting damage due to SLF, but it’s not because of insect feeding damage, Urban said. Quarantine requirements are dragging things down – it’s an economic impact.
Plant nurseries that are shipping in and out of quarantine zones are doing their best to minimize the costs associated with scouting and pesticides, but in SLF hotspots, that can be difficult. In addition, the Christmas tree industry is fighting the pest.
“Just because spotted lanternfly doesn’t feed on conifers doesn’t mean they don’t land on them,” Urban said. Christmas tree growers have to monitor their crops closely because the flies do lay eggs on them.
The sapsucking SLF leaves behind a sticky substance dubbed “honeydew” after it feeds, which often leads to the growth of sooty mold as well as fermenting bacteria and yeast. From late July through early November the fly is in its adult stage and feeding voraciously.
“What they feed upon depends on what’s around them,” Urban said.
But because of their predilection for Tree-of-Heaven, Dr. Robyn Underwood, also of Penn State Entomology, wanted to look at how the pesticide treatment for the plant could impact honeybees. Beginning in 2017, she set up sentinel hives in areas with trap trees in southeastern Pennsylvania. There was concern that when Tree-of-Heaven flowered, pesticides sprayed on it would end up in honey.
Underwood’s research team first looked at spring honey on June 1, made before Tree-of-Heaven would have flowered. They also collected samples on July 21, after the plant flowered and before SLF adults would begin landing on its trunks, and then again on Oct. 11, when SLF feeding would be in full swing.
No dinotefuran (a broad-spectrum insecticide, which is proposed for food uses in/on leafy vegetables and for use in professional turf management, professional ornamental production and in the residential indoor, pet, lawn and garden markets) was detected in any honey sample at any time, despite the very low threshold of 3 ppb.
What was interesting to Underwood was that at first, once the honeydew/leftover sap fermented on the Tree-of-Heaven, bees did not seem interested in it. “They definitely are now” though, she said.
Back in autumn 2019, beekeepers began reporting the gathering of dark, brown fall honey, with a noticeable smoky scent and flavor, not coming from a recognizable source. “The strange flavor appears where spotted lanternfly are established,” Underwood reported.
The cause seemed to be ailanthone (a chemical Tree-of-Heaven – scientific name Ailanthus altissima – makes), which was detected in different samples in amounts of up to 22 ppb. Bees would not have access to ailanthone without SLF.
“The pieces of this puzzle are all pointing to this honey literally being spotted lanternfly honeydew honey,” Underwood said. And that’s not necessarily a bad thing. With that autumn-produced honey, it meant honeybees were gaining hive weight at times they normally wouldn’t. They are increasing in weight at the same time SLF are in great abundance.
Underwood said this is something good coming from a bad bug – “it actually looks like lanternflies are great for bees,” she admitted.
Bees have been overwintering well on this honey for a few years now, which means beekeepers save money on honeybee feed in autumn. As a little bonus, there is also a market for the smoky honey (it’s very popular in the Philadelphia area).
While SLF are still definitely problematic, there is a silver lining to their infestation (or maybe it’s a gold lining, based on what’s being found in honeycombs).
by Courtney Llewellyn