Posts Tagged: varroa mites
And it's an enemy to be reckoned with, Extension apiculturist Eric Mussen told students in the UC Davis "Biology of Parasitism" class, taught by forensic entomologist Robert Kimsey and nematologist Steve Nadler, Department of Entomology and Nematology.
Guest-lecturing at a special session held at the Harry H. Laidlaw Jr. Honey Bee Research Facility, UC Davis, Mussen talked about the varroa mite--its history, biology, damage and control methods--and then opened several hives at the apiary.
The Varroa destructor, a native of Asia, is now found in hives throughout the world except in Australia. It was first detected in the United States in 1987.
The eight-legged reddish-brown parasite, about 1–1.8 mm long and 1.5–2 mm wide, is a blood sucker that's difficult to control, Mussen said. Mites transmit viruses (there are now some 22 named RNA viruses) that can wipe out a hive. A familiar mite-transmitted disease that beekeepers see is DWV or Deformed Wing Virus. Mites are also known lowering the protein level of a bee's blood, and reducing its weight and life span.
Mussen said that mites spread from colony to colony by phoresy (animal-to-animal transport). They ride on flying drones (males) and adult worker bees (females). They also spread changing hosts on flowers.
"A mite enters a honey bee cell just before or during the time it is being capped," Mussen said. "It feeds on older larva or prepupa. Sixty hours later, the mite lays its first egg. The egg will hatch in about 24 hours."
"The number and release of offspring depend on the length of the pupal stage. The queen is pupa for 8.5 days (no mites). The worker is pupa for 12.5 days (1.3 mites) and the drone is pupa for 14.7 days (3 or 4 mites)," he said. Thus, due to the longer time required for drone development, drone pupae get the worst of it.
"When maturing, the newly emerged mites climb onto adult bees and feed by puncturing the intersegmental membranes and sucking the bee blood," Mussen related. "Often these are nurse bees that stay around the brood nest. Sometimes the hosts are drones and older foragers that are flying from the hive every day. Eventually the new mite climbs off the nurse bee onto a comb in the brood nest and enters a cell. The reproductive cycle starts and within 6 days, 44 percent of the young mites have moved into the brood cells; within 12 days, 69 percent of the mites are in the brood cells; and within 24 days, 90 percent of the mite are in the brood cells."
"If there is no brood, the mite has to feed on adult bee blood every six days or so to remain alive," Mussen said. "Mite life expectancy in summer is around 60 days; bees about 42 days. Mite life expectancy in the winter is up to 9 months; bees about six months."
Mussen also discussed how to detect mite infestations through non-chemical and chemical methods, and listed chemical treatments being used throughout the nation. Mites are developing resistance to a few chemical treatments, he pointed out. And, some of the chemical treatments not only kill the mites, but damage or kill the queen and the brood.
Beekeepers who try to go organic, figuring that "if the bees can't make it on their own--if they're not fit--let them die" are really doing a disservice to neighboring beekeepers, Mussen said. The mite will overrun a colony and then infest other colonies.
Public Enemy No. 1--definitely a force to be reckoned with.
Extension apiculturist Eric Mussen (second from left) talks to a UC Davis class in the apiary of the Harry H. Laidlaw Jr. Honey Bee Research Facility. Third from left is forensic entomologist Robert Kimsey, one of the two class instructors.(Photo by Kathy Keatley Garvey)
Extension apiculturist Eric Mussen shows a frame to the students. (Photo by Kathy Keatley Garvey)
Varroa mites are reddish brown. (Photo by Kathy Keatley Garvey)
Extension apiculturist Eric Mussen reaches for a smoker as a bee (far left) buzzes off. (Photo by Kathy Keatley Garvey)
It's a topic we've all been waiting for: "Honey Bee Health and Disease Resistance."
Jay Evans, a research entomologist with the USDA's Agricultural Research Service (USDA-ARS) Beltsville Bee Research Laboratory for the past 14 years, will discuss "Bee Disease Resistance and Colony Health" on Wednesday, Oct. 2 to open the fall seminar series hosted by the UC Davis Department of Entomology and Nematology.
His lecture, open to all interested persons, is from 12:10 to 1 p.m. in Room 122 of Briggs Hall, located on Kleiber Hall Drive, UC Davis campus.
"Honey bees are vulnerable to poor nutrition, parasites and pathogens, and exposure to chemicals," Evans said. "These threats can occur in batches and little is known about the impacts of multiple challenges to honey bee health, and about the abilities of bees to fend off these threats. I will present recent work aimed at determining the impacts of multiple parasites on bee health. I will also discuss the impacts Varroa mites, chemicals, and bacterial symbionts on bee health and colony losses."
As a research entomologist, Evans has focused his projects on a range of bee pests including bacteria, fungi, viruses and, mites, and beetles. He is especially interested in the immune defenses of bees toward these threats.
Evans was an early proponent of the Honey Bee Genome Project and helped recruit and organize scientists interested in applied genomics for bees. He has improved and applied genetic screens for possible causes of colony collapse disorder and is now heading a consortium to sequence the genome of the Varroa mite in order to develop novel control methods for this key pest.
Evans holds a bachelor's degree in biology from Princeton and a doctorate in biology from the University of Utah.
The fall seminars, coordinated by faculty members Joanna Chiu and Brian Johnson, will be held every Wednesday noon through Dec. 11 in 122 Briggs Hall, except for Nov. 27, Thanksgiving Week, when no seminar will be held.
Under the coordination of professor James R. Carey, all seminars are to be videotaped and posted at a later date on UCTV.
Anyone with a computer can view the seminars, and yes, they're free.
Inside the hive. (Photo by Kathy Keatley Garvey)
Varroa mite on a drone pupa. (Photo by Kathy Keatley Garvey)
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