Posts Tagged: varroa mites
The California Gold Rush (1848-1855) has nothing on honey bees.
Sometimes foraging honey bees are covered with their own kind of gold--pollen--or protein for their colonies.
We saw this honey bee dusted with gold from head to thorax to abdomen as she gathered pollen from blanket flowers (Gaillardia). Her flight plan seemed uncertain, as her load was heavy and her visibility, poor. She struggled to take off, but take off she did.
Speaking of the Gold Rush and honey bees, entomologists always associate the arrival of honey bees in California with the California Gold Rush. That's because honey bees were introduced to California in 1853, right in the middle of the Gold Rush.
Back then, the hills were covered with wildflowers where bees gathered nectar (carbohydrates) and pollen (protein). Today, however, scientists are worried about bee malnutrition.
"Honey bee colonies need a mix of pollens every day to meet their nutritional needs," says Extension apiculturist Eric Mussen of the UC Davis Department of Entomology and Nematology. "In fact, they should have a one-acre equivalent of blossoms available to them daily to meet their demands. They can fly up to four miles from the hive--a 50-square mile area--to gather that food and water (and propolis, plant resin)."
A worried beekeeper recently asked him about the declining bee population and wondered why his own colonies were dwindling. In addition to malnutrition, Mussen listed a few other possibilities:
Varroa mites – "They suck the blood from developing pupae and adult bees, shortening their lifespans. They vector virus diseases, the easiest to see being deformed wing virus. If you have adult bees around the colony with curly, undeveloped wings, then you have too many mites. If you see mites on the bees when you look in the hive, that is too many mites."
Nosema ceranae and other diseases – "You need a microscope to see the spores of a Nosema infection. Go to Randy Oliver’s webpage, Scientificbeekeeping.com, and look at the information on Nosema ceranae and spore counting."
Contact with toxic chemicals – "Since your bees can fly up to four miles away to forage, that also is the distance within which they can get into trouble with bee-toxic chemicals. It is not likely that the organic farm is a source. However, if there are other farms around, or if your neighbors (golf courses, shopping centers, parks, playgrounds, etc.) are having problems with sucking or chewing insects, they may have used one of the neonicotinoids on their shrubs or trees. Turf and ornamental dosages are considerably higher than those used in commercial agriculture. So, the amounts of toxins in nectar and pollens can be toxic to honey bees and other pollinators."
Mussen also acknowledged that California buckeye blossoms are toxic to bees. "This was a fairly dry spring," he said. "Not too many weeds and wildflowers were around when the California buckeye came into bloom. Buckeye pollen is toxic to developing bee brood and to adult bees, if it gets to be their primary food source in the colony."
The problem could also be due to other issues as well, Mussen said. "Maybe the queens did not mate with enough drones, or the queens got too hot or too cold during their journeys to your hives, etc."
"As beekeepers, it is up to you to stick your nose in the hive, look at everything and try to determine what may be going wrong. If you are feeling way too new at this to have any idea of what is going on, then contact your local bee club--there is one in practically half of the California counties--and find someone to help access your problems."
And the pollen, that precious protein? "When beekeepers examine their hives, they should see a good supply of pollen with many colors," Mussen says.
Honey bee is covered with pollen from a blanket flower, Gaillardia. (Photo by Kathy Keatley Garvey)
Honey bee is dusted with pollen from the blanket flower. (Photo by Kathy Keatley Garvey)
Lift off? The bee struggles to take off. (Photo by Kathy Keatley Garvey)
Varroa mites, those pesky little parasites that suck the blood out of honey bees and spread multiple viruses, are now found throughout the world, except in Australia.
Scientists blame these parasites as one of the causes of colony collapse disorder (CCD), characterized by adult bees abandoning the hive and leaving behind the queen, brood and food stores. They attribute CCD to a multitude of factors, including pests, pesticides, parasites, diseases, viruses, malnutrition and stress. Thus, varroa mites are a key factor in the declining honey bee population.
Today's honey bees are ill-equipped to rid their hives of a varroa mite infestation. Indeed, beekeepers consider the varroa mite (scientific name Varroa destructor) as Public Enemy No. 1.
And that's one of the reasons why we like bee breeder-geneticist Susan Cobey's efforts to increase the genetic diversity in our domestic honey bee gene pool.
Cobey, who has a dual appointment at the University of California, Davis and Washington State University, is directing a stock improvement program which aims to do just that.
"Increasing the overall genetic diversity of honey bees will lead to healthier and hardier bees that can better fight off parasites, pathogens and pests," she says.
"We have collected and imported honey bee semen (germplasm) from their original European homeland to inseminate select domestic queens produced by the California bee breeders," Cobey told us. These California breeders supply queen bees and package bees nationwide. Honey bees, as Cobey points out, "provide the essential pollination for our crops, especially in California, "the breadbasket" of our country and our world.
Cobey and her team have also re-introduced the subspecies, Apis mellifera caucasica, a dark race of bee known for its collection and use of propolis, self-medicating plant resins.
What does a mite look like? Check out the mite-infested drone below. A boy bee's only duty is to gather in the drone congregation area and mate with the queen during her maiden flight, but that won't happen with this one. No thanks to the parasitic mites, he has a weakened immune system, crippling his ability to fly.
What will happen to him? His sisters will kick him out of the hive and he will die.
The lifespan of this mite-infested drone will be short. The brownish-orange "bumps" are varroa mites. (Photo by Kathy Keatley Garvey)
Close-up of varroa mite on drone pupa. (Photo by Kathy Keatley Garvey)
To a beekeeper, it's a four-letter word.
Specifically, the varroa mite, also known as Varroa destructor.
It's a small (think flea-sized) crab-shaped parasite that feeds on bees, either in the brood (immature bees) or on adult bees.
Extension apiculturist Eric Mussen, member of the UC Davis Department of Entomology faculty, just updated his Bee Brief on this blood sucker. His Bee Briefs, all posted online on the department Web site, can be downloaded for free.
This Bee Brief is titled "Treating Colonies for Varroa Mite Infestations." (You'll also want to read his updated colony collapse disorder (CCD) Bee Brief.)
It's apparent, Mussen says, that resistant mites are now prevalent in the United States, including California.
"Chemical testing has demonstrated that varroa mites commonly are resistant to fluvalinate, coumaphos and amitraz. Losses of wintering colonies were over twice as high as 'normal' during the early 2000s, with one of the worst losses (40 to 60 percent) of California (and total U.S.) commercial colonies over the 2005-05 winter. Infested colonies dwindled away during the fall and winter."
Meanwhile, a hive without a varroa mite is a scarcity indeed.
You can see varroa mites on the larva (below) and on an adult bee.
Just think if you had a blood sucker on you like that.
Mite on Pupa
Those dratted mites.
UC Davis entomologist Robbin Thorp, emeritus professor and a native bee pollinator specialist, sent us a BBC report linking a varroa mite infestation to a devastating honey production loss in the UK. It's the worst honey crisis ever to hit the UK.
In short: beekeepers are concerned that by Christmas, there may be no more domestically produced honey left on the supermarket shelves.
The mite infestation has already killed off an estimated quarter of the UK's honey bees, according to BBC correspondent Jeremy Cooke, who said about "one in three colonies has been wiped out."
The varroa mite, or the Varroa destructor, is a nasty pest. Now found in most countries (Australia is an exception), it's an external parasite initially discovered on the Asian honey bee, Apis cerana. Over the last few decades, however, it has spread to the Western honey bee (also known as the European honey bee), Apis mellifera.
The varroa mite entered the UK in 1992, reports show. It has since spread throughout England, Wales, Scotland and Northern Ireland.
The blood-sucking parasite feeds on both adults and the brood (immature larvae). It weakens the bees, opening them up to all sorts of diseases. And eventually, if not controlled, it will destroy the colonies.
The bad news is that the varroa mite cannot be completely eradicated, but with proper control methods, the mite population can be kept at a low level.
When California State Secretary of Agriculture A. G. Kawamura visited the Harry H. Laidlaw Jr. Honey Bee Research Facility at UC Davis last month, bee breeder-geneticist Susan Cobey showed him dead mites on a hive floor. (See story on UC Davis Department of Entomology site.)
Kawamura is no stranger to bees or bee pests. As a youth, he reared bees--until the infectious bee disease, American foulbrood, upset his plans.
To control the mite, beekeepers usually use a combination of management methods. They use biotechnical methods and chemical controls. Unfortunately, in some areas, the varroa mite is developing resistance to miticides--another worry for beekeepers.
Said Cobey: "You need to reduce mite levels in colonies by late summer--August/September--to have healthy bees in spring."
Cooperative Extension apiculturist Eric Mussen of UC Davis says that in California, the Department of Pesticide Regulation "is close to approving another chemical treatment" to help control the mite problem.
It may be ready by next spring.
The mites will be waiting.
Mite on Drone
Mites on Hive Floor