Ron Wilson

Ron Wilson

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First Giant Asian Hornet Nest Destroyed

The Asian Giant Hornet (AGH) (Vespa mandarinia) is the world's largest hornet with a body length of 1.5 – 2" and a wingspan from 1.5 – 3". The hornet's other notable features beyond its huge size are itslarge orange or orangish-yellow headanddistinct orangish-yellow and reddish-brown bands on its abdomen.

The hornet hasnot been found in Ohio. But beekeepers must be vigilantbecause this so-called "murder hornet" is murderous on European honey bees (Apis mellifera). Beekeepers who discover hives that have been suddenly wiped this fall for no apparent reason should contact our Ohio Department of Agriculture (ODA).

First Nests Found in North American are Destroyed

The first Asian Giant Hornet (AGH) (Vespa mandarinia) nest found in the U.S. was destroyed by Washington State Department of Agriculture (WSDA) workers in the pre-dawn hours this past Saturday, October 24. The nest had been found last Thursday on private property in Blaine, WA, just south of British Columbia's Peace Arch border crossing. Locating and destroying AGH nests are key steps in eradicating this destructive non-native wasp.

The WSDA acted quickly because AGH nests produce males and new reproductive females (queens) in late October and November. The new queens mate and spend the winter in protected sites. Next spring, each new queen will establish their own new nest. Destroying nests now reduces the number of new nests next year.

The WSDA, USDA Animal and Plant Health Inspection Service (APHIS), and the British Columbia (BC) Ministry of Agriculture have remained keenly vigilant for AGH ever since hornet workers were found last year on Vancouver Island, BC, and just across the international border in the northwest corner of Washington. Indeed, the BC authorities destroyed an underground AGH nest in Nanaimo on Vancouver on September 18, 2019. It was the first AGH nest found in North America.

The WSDA and the BC Ministry of Agriculture have been successfully using "bottle traps" and visual sightings by the public to detect AGH workers. Raids on honey bee hives in the Blaine, WA, region also revealed there was at least one AGH nest in the region. However, AGH raiders and foraging workers may fly far from their nests.

The AGH nest found on Vancouver Island, BC, was located in the ground in an urban park. Thus, it was discovered through observations made by government officials and the public. However, AGH may also nest in trees in wooded areas making them more difficult to find.

Nest Location: Ground Control to Major Tom

Using radio telemetry to track the movement of animals is not a new concept. However, there's a big difference between attaching a radio transmitter to an elephant compared to an insect.

Tiny radio transmitters were supplied to the WSDA by the USDA APHIS' Otis Pest Survey, Detection, and Exclusion Laboratory in Cape Cod, MA. The radio-telemetry tags had originally been used to track another non-native insect, the spotted lanternfly (Lycorma delicatula).

WSDA workers attached the telemetry tags to live-trapped hornets. Of course, the hornets were anesthetized to avoid damage to both the capturers and the captured. They then radio-tracked one of the tagged hornets back to the nest. It was an important proof-of-concept for locating AGH nests.

The nest was in a large, dead tree in the backyard of a private residence. Its destruction involved several steps aimed at both preventing hornet escapes as well as protecting the WSDA workers. The workers donned special suits designed to keep the 1/4" long AGH stingers away from the workers.

The nest tree is wrapped in cellophane and then a vacuum was used to suck the hornets through a single hole into a container. Next, the coup de grace was delivered by pumping CO2 into the nest at a lethal dosage. This was done on Saturday. They took the tree down yesterday for a further close inspection presumably as someone plays taps for the hornets that are no more.

What's at Stake?

Despite the social media hype and dubious web postings, experts consistently note that AGH is not particularly hostile towards humans, pets, and large animals. As with our native bald-faced hornets (Dolichovespula maculata), yellowjackets (Vespulaspp.), and paper wasps (Polistesspp.), AGHs generally goes about its business unless its nests are threatened. Theirvenom is not any more toxic than our native wasps; however, they deliver a bigger dose which increases the risk for anaphylactic shock. Still, if left alone, they will leave people alone.

However, the giant hornets are voracious meat-eaters. They'll attack and eat any insect they can get their mandibles around. Indeed, they're very territorial and will even attack one another if AGH nests fall within overlapping territories.

In late summer to early fall, AGHs change their behavior; dramatically. They morph from mild-mannered colonies going about their business into a rampaging meat-gathering horde guided by scouts that locate victims. This change is known as the "slaughter phase."  

European honey bees are a favorite target. To the hornets, honey bee hives are all-you-can-eat buffets. AGHs will mass-attack honey bee hives and quickly dispatch the workers/guards primarily by clipping off their heads. They can destroy an entire beehive within a few hours after initiating a mass-attack.

Surprisingly, they're not after the honey; it's just icing on the cake. Their real prize in attacking beehives are the fat, juicy honey bee larvae, and pupae reposing in their wax cells.

The murderous hornets pull their helpless immature honey bee victims from their cells and fly their prize back to their nests to feed themelliferameat morsels to the newly developing males and queens. It's believed the honey bee treats provide energy to help the new queens survive the winter which may be why the bee-raiding slaughter phase primarily occurs in late summer to early fall.

Loss of honey bee hives would be catastrophic to the commercial pollination industry. It would also be disastrous for our food supply. Beekeepers should be particularly vigilantgiven that they are on the front lines in monitoring for AGH in Washington State. In fact, so-called "sentinel hives" were developed by WSDA in an effort to discover AGH activity.

Also, if AGH were allowed to run rampant in North America, they would compete directly with our native wasps. Keep in mind that yellowjackets, bald-faced hornets, and paper wasps are not only meat-eaters like AGH, they are also pollinators; particularly the paper wasps. They provide a two-for service in our natural and landscape ecosystems.

If You See It Report It!

Our Ohio Department of Agriculture (ODA) created an AGH Reporting Tool earlier this season so Ohioans canprovide photographs and locations of suspicious insects. Although photographs can't serve as official confirmation, they are very helpful in making an initial identification before opening an investigation.

Thus far, the most common wasp reported in Ohio using the ODA Reporting Tool has been the non-native European Hornet (V. crabro). However, do not use the picture below to prevent you from reporting! You shouldreport any suspicious-looking insect.

Click this hotlink to report suspicious-looking insects using the ODA Asian Giant Hornet Online Portal:

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