Don't worry yet about 'murder hornets' in N.E., at least not yet

Asian giant hornet

— Photo from Washington State Department of Agriculture

From ecoRi News (ecori.org)

News of the arrival in North America of a non-native insect with the terrifying colloquial name of “murder hornet” has alarmed residents nationwide. But a University of Rhode Island entomologist said there is little reason for Rhode Islanders {and thus by implication New Englanders in general} to worry about them.

Two murder hornets, which are more appropriately called Asian giant hornets, were discovered in Washington State in December shortly after a nest was discovered in nearby British Columbia. Native to Japan, where they are responsible for about 50 human deaths annually, the 2-inch-long insects with orange heads and black eyes are best known for their foraging behavior of ripping the heads off honeybees and feeding the rest of the bees’ bodies to their young.

“Their reputation as murder hornets comes from the fact that they can kill a lot of honeybees in a very short period of time,” URI entomologist Lisa Tewksbury said. “The major concern about their arrival in North America is for the damage they could cause to commercial honeybees used for pollinating agricultural fields. They are capable of quickly destroying beehives.”

Tewksbury said the hornet’s sting isn’t any more toxic than that of the bees and hornets commonly found in New England, but because of their large size, Asian giant hornets can deliver a larger dose of toxin with each sting. They are a danger to humans only when stung multiple times, according to Tewksbury.

“But they’re not known to aggressively attack humans,” she said. “It only happens occasionally and randomly.”

Rhode Island is home to two hornets similar in size to the Asian giant hornet: the cicada killer wasps, which dig their nests in sandy or light soil in areas such as athletic fields and playgrounds, and the European hornet, a non-native species that has become naturalized in New England after its arrival here in the 1800s. Like the Asian giant hornet, they are among the largest wasp-like insects in the world.

Tewksbury said that it’s extremely unlikely that the Asian giant hornets in the Pacific Northwest are in Rhode Island or likely will be soon. The concern is that no one knows how the hornets made it to Washington.

“We don’t know the pathway it took to get to Washington, and since we don’t know, it’s difficult to know how to prevent further introductions into North America,” she said.

Although she noted that Rhode Islanders need not be concerned about murder hornets, she advises residents to keep their eyes out for any unusual insect they’ve never seen before, since non-native insects do occasionally arrive in the region.

If you spot an unusual insect, Tewksbury said, take a picture of it and report it to the Rhode Island Department of Environmental Management’s invasive species sighting form.

Using Ukrainian moths to control invasive vines

Swallow-wort, a highly invasive vine from Europe that reduces Monarch butterfly populations.

The Hypena opulenta moth. It eats swallow-wort.

Via ecoRI News (ecori.org)

KINGSTON, R.I.

After more than 10 years of research, scientists at the University of Rhode Island’s Biocontrol Laboratory have released a species of moth collected from Ukraine to help control invasive black and pale swallow-worts.

Swallow-worts are invasive vines native to Europe that were introduced into North America in the 19th Century, and quickly spread along the East Coast and into Canada. Not only do they outcompete native species and alter soil chemistry, but they harm Monarch butterfly populations. Because swallow-wort is so closely related to milkweed, Monarch butterflies lay their eggs on swallow-wort leaves, but when the eggs hatch the larvae are unable to survive on the plant.

“Swallow-wort was one of those weeds becoming increasingly problematic,” said Aaron Weed, of Tunbridge, Vt., a former Ph.D. student at URI who spearheaded the project. Back in 2005 when Weed started his research as a URI graduate student, there was increasing interest in controlling swallow-worts. Since then, he’s seen the vine spread aggressively. It thrives in several different environments, including pastures, forests, and urban spaces.

“Integrated management of weeds is a very challenging endeavor,” Weed said. “Biocontrol is potentially efficacious for swallow-wort because conventional methods just weren’t working or were incompatible in sensitive areas.”

Weed traveled to Europe to try and find natural enemies of swallow-worts and brought back several insect species to test at URI’s Biocontrol Lab. Among them was the Hypena opulenta, a small moth collected from southeastern Ukraine, that the lab found feeds exclusively on swallow-wort species. Weed worked with Lisa Tewksbury, URI’s Biocontrol Lab manager, and Richard Casagrande, professor emeritus of entomology at URI, to conduct years of research on the biology of Hypena opulenta and its impact on swallow-worts.

Hypena opulenta was a suitable candidate because it uses swallow-wort exclusively as its host plant, and reproduces several times a year. Its larvae have the potential to cause significant harm to the plants, according to Tewksbury.

URI received the permit to release the moths in 2017, and field tests in controlled cages were conducted in Charlestown, R.I., and in Massachusetts last year. Tewksbury has been monitoring the releases, and if they’re successful, she said the lab plans to work with other local agencies to share resources and release the moths in other areas.

Tewksbury’s lab found the first moth that emerged in June, but hasn’t seen any others yet emerge. Tewksbury hypothesized that Rhode Island’s unusually cool temperatures throughout June may have delayed the moths’ emergence. She also noted that this is the first time that we’re seeing the emergence of this species in New England.

“The goal of biological control is to reacquaint new pests with their historical natural enemies,” Tewksbury said. “This restores the evolutionary relationship of an insect with its host plant, which we hope will provide long-term management of the invasive plant species.”

Continued research is underway to assess how well this insect will control populations across New England.

“Since insects are impacted by the health of their plants, the local climate, and the health of plants is affected by site conditions, we still need to determine under which site conditions biocontrol impact is likely to lead to weed suppression,” Weed said.

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