Varroa Eradicated from Guam

Text of the article

ARTICLE BY KRIS FRICKE

I made a shocking discovery the other day … which was that Christopher Rosario made a shocking discovery a few years ago. I was browsing through a

recent issue of Entomology Today1, as one does, and there was an article that mentioned Guam state entomologist Christopher Rosario had “eradicated an

invasive parasite,” but didn’t mention which one.

Eradicating an invasive parasite is always a worthwhile activity so I thought I’d contact him to find out what he had eradicated.

“Varroa mites” he wrote back.2 I about fell out of my chair. I recovered myself, repeating surely, surely it was just the less dangerous “Varroa jacobsonii” though. So I asked him. “Varroa destructor,” he said. For the next few days “have I told you about Guam??” was all I could say to anyone.

Now before I tell you his story, let me tell you about Guam. Guam is a small island in the west Pacific about 2000 kilometres east of the Philippines and 1900 north of Papua New Guinea, which is to say really far from the nearest “mainland” of any kind. The island is 549 square kilometres, which would nicely fit within Port Phillip Bay, and has a population of 168,801, which convenient for comparison is almost exactly the same as the population of the Mornington peninsula on the east side of the comparison map in Fig 1. The population of Guam is relatively concentrated in the north, with the population of the more rugged south mostly limited to coastal villages. The south has, according to Rosario, mostly lots of rivers, ponds, and waterfalls, and having googled it myself, the waterfalls look very pretty. Also relevant to our story here, Guam is not entirely alone in the Pacific, the Commonwealth of the Northern Mariana Islands (CNMIs) are another cluster of islands of which the main islands are 75-200 kilometres north of Guam. Honey bees are, of course, not native to Pacific Islands. Apis mellifera ligustica, the italian bee, was first introduced to Guam in 1907 from Hawaii*, with some follow up importations of more bees until in 1954 the Organic Act of Guam was signed, which banned further importation of honey bees to Guam. The Northern Mariana Islands continued to import bees from Hawaii until 2010 … varroa had arrived in Hawaii in 2007.5

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Fig 1 Guam fits snugs in Port Philip Bay, & has has almost exactly same population as that of the Mornington Peninsula

on the east side of the bay. Map data © 2024 Google.

Which brings us to our story. Christopher Rosario, a native of Guam, had graduated the University of Guam in 2012 with a Bachelor’s degree in biology and wanted to become a veterinarian. In 2013 he found a job opening as a field technician conducting the Project APHIS (USDA Animal and Plant Health Inspection Service) National Honey Bee Survey (NHBS†) to see if Varroa or Tropilaelaps mites were present in Guam and the Northern Mariana Islands. He did not have a background in beekeeping and was initially afraid of getting stung to death, but he had a lot of debt from his bachelor’s degree and veterinary school would only have added to it, so he applied for and got the bee survey job.

The NHBS wanted him to survey 24 apiaries, but there was a problem: there were only four established apiaries on the island! He put word out in the local news requesting the public to call in feral colonies, and soon three to four times

The honey bee colonies in the initial APHIS survey, line pointing at the initial detection,

with second detection near it.

a week people were calling him to remove colonies from their homes, or asking how to start keeping bees.

In March 2014, near the village of Malesso beside the Cocos Lagoon he was called out to a large exposed colony eight metres up in a monkeypod tree (Samanea saman) (Fig 2). Up he went in a cherrypicker lift to reach the colony, calmed the bees with a smoker, and swept up flying bees around the colony with an insect net until he had about a quarter cup (60ml) of bees. The bees were then funnelled into a bottle with ethanol, to be sent back to the University of Guam for analysis. Job done, down he went and on to the next site, he was just a technician after all, it was for the lab to analyse. Altogether he took samples on Guam from 18 feral colonies and two domestic hives.

Then he proceeded to the Northern Mariana islands of Saipan and Tinian, where they sampled four colonies and three of them immediately, obviously, were positive for varroa – “mites were crawling out of the bottle!” Rosario says.

Back in Guam a month went by before he heard anything more about that exposed colony beside the lagoon. Then he got the bad news in a call from his boss, the then state entomologist of Guam, Dr Russell Campbell. That and one other feral colony also on the southern coast had both tested positive for low levels (1-2 in the sample) of mites.

“I had no idea how bad they were until I was told that the bee colony needed to be eradicated” Rosario relates, “I was a student fresh out of college that did not know anything about honey bees [or their pests].”

The territory’s entomologists were all understandably shocked. This hive would need to be put down immediately! Fortunately they had a Coconut Rhinoceros Beetle eradication team led by invasive species specialist Roland Quitugua, with a truck-based insecticide sprayer and 200 litres of cypermethrin. “It was so saddening to watch,” Rosario says of seeing them hose down the colony.

Two sentinel hives were then put near the area and monitored. Nothing else was found until the following year mites were detected in one of the sentinel hives. Again from lab analysis (because a low level mite infection is unlikely to show in an alcohol wash, here in Australia, samples from sentinel hives are also sent for lab analysis6 and that’s how mites were first detected in June 20227). Despite doing alcohol washes at the time of sample taking, “I have yet to witness a mite in a bee colony in Guam” Rosario says, as all detections have been at such low levels they were only caught in the lab.

Two colonies with varroa were detected in 2016, and one in 2017. All were eradicated (“It was then that I learned to do euthanasia with soap and water”). Since 2017, despite constant monitoring, no mites have been detected.

Rosario believes the mites had probably come from the

Also Rosario, the Guam Department of Agriculture, and the University of Guam have been promoting managed beekeeping, so that local beekeepers will spot and report any further exotic pest incursions. When Rosario began surveying in 2013 there were only three beekeepers in Guam. As a result of his public calls to report bees, he was hearing from all these people who either had bees or wanted to get into beekeeping. He noticed “a harmony between people wanting to get rid of bees on their property, and people wanting to keep bees on their property.”1 So he rehomed the unwanted bees to the people who wanted them.

Fig 2 Gu-12, the first detection.

The small community of beekeepers grew by about ten a year, jumping from 55 to 105 during Covid as interest in hobbies one can do at home peaked. Now there are 115 beekeepers in the Guam Beekeeper’s Association (https://www.guambeekeepers. org/) managing about 250 hives, including six beekeepers commercially selling their honey. Rosario estimates that for every managed hive, however, there are 10 feral hives (which would equal 4.4 hives per square kilometre, which incidentally exactly matches Australian estimates (see Letters, last issue)).

This push for people to call in about bees may have helped detect another invasive pest – in June 2016 someone called in a bee colony that turned out to be something much worse. By the shores of clear and shallow Tumon Bay in the northern built-up part of Guam, where the Hyatt and Hilton overlook the beach, Rosario was called to look inside a hollow old avocado tree. There he found not a bee colony but an ugly

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Northern Mariana Islands, where varroa is pervasive. Despite the import of bee stock being illegal, it is believed someone had smuggled bees in from the CNMIs or Hawaii, either by boat or air cargo.

Rosario sees a real Varroa mite up close for the first time, looking at the sample from Tinian Island back at

University of Guam’s Bioquarantine Lab.

nest of several tiers of dark paper mâché filled with bright white pupal cocoons like an arsenal of missiles ready to launch, and covering this and flying around it were large inch-long brown hornets with a single broad yellow band around their abdomen: the Greater Banded Hornet, Vespa tropica. Soon they were being found all over the island, it was already too late to prevent them from taking hold.8

It’s believed the hornets came in an empty cargo container on a ship from Southeast Asia. Rosario, sensing what a threat this species was, was “extremely devastated” when he found the hornets. Other entomologists assured him they weren’t a pest of honey bees, but that sadly proved untrue. These hornets’ first preference for prey is paper wasps, and the island’s wasp population (Polistes olivaceus, & Polistes stigma**, known locally as “boonie bees”) immediately crashed. Running out of wasps to eat, the hornets turned to bees, and 55 managed colonies have been lost to hornets to date (one out of every six hives!).

Guam is so far free from Foulbrood (EFB or AFB), or small hive beetle, though they do suffer from Chalkbrood due to the high humidity.

Guam does not have any specific biosecurity officers. In 2003 the Plant Protection Quarantine officers they had had were merged into the Guam Customs and Quarantine “which essentially gutted the Department of Agriculture’s biosecurity program” (As Dr Campbell put it). Today the Guam Department of Agriculture, Customs and Quarantine Agency, and US Department of Agriculture APHIS Plant Protection Quarantine work together for management and prevention of invasive species. It is estimated that every year a hundred invasive species arrive in Guam via the ports, with three successfully establishing themselves.1 Coconut rhinoceros beetles (Oryctes rhinoceros), little fire ants (Wasmannia auropunctata), and Asian Cycad Scale (Aulacaspis yasumatsui) (an insect which attacks Guam’s native Cycas micronesica, a ferny plant) are a few examples of other invasive pests that have unfortunately become established. The rhinoceros beetles have destroyed over half the island’s coconut trees.

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Chris Rosario, you will recall, had wanted to be a veterinarian when he found work as a technician in the honey bee survey. “This survey opened my eyes to research because so little was known about honey bees in Guam. It then made me want to go into graduate school, where I used this survey as my research project,” Rosario told Entomology Today1. In 2021 he received his Master’s Degree in environmental science with a focus on entomology. His boss, Dr Campbell, happened to be retiring, and Rosario successfully applied for the position, becoming the first native of Guam to be the island’s state entomologist.

REFERENCES *. Where bees had arrived in 1857 from California,3 where bees had only arrived in 18534, but I digress †. https://ushoneybeehealthsurvey.info/ **. These wasp species were themselves introduced via Japanese vessels in WWII 1. Serrano, J (2024) “How One Entomologist Works to Combat Invasive Species and Protect Honey Bees on Guam” Entomology Today https:// entomologytoday.org/2024/03/25/entomologist-invasive-species-honeybees-guam-christopher-rosario-standout-early-career-professional/ 2. All otherwise uncited quotes and details: from personal communication with Christopher Rosario June and July 2024 3. Roddy, K., Arita-Tsutsumi, L., (1997) “A History of Honey Bees in the Hawaiian Islands” Journal of Hawaiian and Pacific Agriculture Volume 8 No 1 https://hilo.hawaii.edu/panr/writing.php?id=198 4. Harbison, J.S. (1919) “Introduction of the Honeybee to California” American Bee Journal (59)9: 268-270 5. Prendergast, K., (2017) “Mites Hawaii and the Varroa Mite: A case study” https://blythewoodbeecompany.com/blogs/news/mite-in-hawaii-and-thevarroa-mite-a-case-study 6. Huntsdale, J., (2018) “Sentinel Beehives Provide Coastal Defence Against Catastrophic Varroa Mite Invasion” Australian Broadcasting Corporation Feb 23rd https://www.abc.net.au/news/2018-02-23/sentinel-bee-hiveprogram-defending-against-varroa-mite/9470992 7. Hilton, A., (2024) “Varroa mites have infested honey bee hives across NSW. The fight is on to contain their spread to other states” Australian Broadcasting Corporation July 6th https://www.abc.net.au/news/2024- 07-06/states-battle-against-varroa-mite-spread/104014530 8. Rosario, C., (2018) “Greater banded hornet (Vespa tropica) established at several locations on Guam” [poster presentation] Meeting of the Entomological Societies of America, Canada, and British Colombia, Vancouver, BC, Canada

Christopher Rosario with a swarm reported

by a resident,

Christopher Rosario and apiary

inspectors from across the US made

their way to Thailand for a

Tropilaelaps detection workshop

conducted by Auburn and Chiang

Mai universities, and funded by the North Dakota Dept

of Agriculture and

Project Apis, in

January 2024.

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