In our lab, we benefit from a diverse repertoire of individuals coming from varied backgrounds. Working at a university includes the benefit of having motivated students with unique skills ready to use their talents. Byron Mariani, a Sophomore Kinesiology Major, is one of these students who began working at the Bee Informed Partnership Lab at the beginning of the fall 2013 semester. In addition to the help he provides in diagnosing colonies for Varroa, he has also proven himself invaluable with his video editing abilities. With the help from our undergraduates, Anthony Nearman who provides a voice-over, and Kirsten Traynor who wrote the script, we are proud to release a new short video on Varroa Mites and the processing we conduct on mites from samples we receive from the field.
Varroa destructor is a parasitic mite that infests honey bee colonies by living off the hemolymph of honey bees. The Varroa mite has had the most pronounced impact on the honey bee and beekeeping industry compared to any other parasite or disease. This video provides a short overview of the honey bee life cycle and the evolving relationship that has occurred between Varroa destructor and Deformed Wing Virus (DWV). In addition, this video also explores the standardized techniques we use to diagnose colonies for Varroa mites at the Bee Informed Partnership.
The most opportune time for honey bee colonies in most areas of the U.S. is during spring build-up. The surplus of pollen and nectar that usually accompanies spring allows a growing colony to create a surplus of pollen and honey. It is also a time of year where the colony is trying to work through its kinks and get the colonies population dynamics under control as far as nurse bee to worker ratio. This ratio is crucial for hive ventilation and keeping moisture and bacteria from infiltrating the hive and causing problems. Some diseases that arise during this opportunistic time period are Chalkbrood, AFB, EFB and PMS. It is important to recognize these problems early as it may save your honey crop and the headache of trying to support the colony through the summer.
Other problems during this time include overcrowding/swarming or queen supercedure. A good indicator that a colony is going to swarm is the sudden increase in drone cells. This may be in the form of bridge comb or general drone laying production. It is best to treat colonies in early spring for varroa mites before the colony starts to produce excess drone cells. Once you start seeing a lot of drones it’s a good time to keep your eye out for swarm cells. These cells are a great way to split a colony and create more colonies from existing ones. You can also induce swarming by overcrowding the bees and feeding them pollen and thick sugar syrup.
These are all common occurrences during the spring, but the main reason I wanted to write this blog was to share some of the things that I have seen in the field and create an opportunity for you to recognize these symptoms early on. I hope that by viewing these images, you will be able to identify possible disease or pest and seek the appropriate actions in controlling them. Below are images from this spring, the good, the bad and the ugly!!
Typically when critter infestations come up into beekeeping conversation these common mammals come to mind: bears, skunks, mice, opossums and raccoons. Just like their size, pygmy shrews often fall under the radar. However, Fletcher Colpitts, Chief Apiary Inspector of New Brunswick, Canada, is working to make information about the pygmy shrew more available. He recently posted an info sheet about the pygmy shrew that every beekeeper should read: http://www.nbba.ca/wp-content/uploads/2014/03/shrew_screen.pdf
The pygmy shrew is the smallest mammal native to North America. It can fit through a hole in a honey bee hive as little as 1 cm, and surprisingly only weighs an average of 3 grams. Although they are tiny, pygmy shrews are also extremely fast, and consequently have a high heart rate of 800 bpm. In order to support their high respiratory rate they must eat on a constant basis (at least every 15 or 30 minutes) during the day and night. If they go more than an hour without eating they are at risk of dying of starvation.
They are generalist insectivores, but in northern climates (eastern Canada) they have learned to seek out honey bees for nourishment. Shrews become a problem in the early spring when bees are still tightly clustered due to low temperatures. They feed on colonies by grabbing a bee from the outside of the cluster where it’s colder. Bees on the outside of the cluster are sluggish and unable to defend themselves against the shrew invader. The shrew will then carry its prize away from the cluster and move to the bottom of the frame or sometimes near the top under the inner cover. There it will remove the head and tunnel into the thorax using its pointed snout to consume the contents.
So, how do you identify if a shrew has invaded your colony? And how do you tell shrew damage apart from mouse damage? To answer these questions I contacted Fletcher Colpitts, and I was fortunate enough to interview him over the phone. He told me that pygmy shrews can be identified by the mess they leave and their feces which differ from mice. The shrew will leave a “trash” pile as Fletcher called it (appropriately named) of heads, wings and legs. At first glance, shrew feces looks very similar to mouse feces, however it is much different if inspected more closely. Pygmy shrew feces are elongated with irregular diameters (rough looking).
It is also important to note that shrews will never nest in hive boxes and will never be found during the summer months as mice sometimes are. As temperatures rise honey bees begin to be able to defend themselves so shrews will leave. The primary food source in the hive for mice is pollen and honey; however shrews will only target the honey bees themselves. On occasion, shrews will die in the hive, which is the best evidence you will find.
Occasionally, shrews will become immediately apparent as Fletcher Colpitts discovered. While watching his colonies very intently, he noticed a shrew (not so much a form, more like a gray flash). These little creatures move so fast, much faster than a mouse, that it is very difficult to spot them, but definitely possible. Further confirmation was observed in the form of a headless bee walking out of the entrance of the hive.
Last year was one of the worst years for shrew damage for a major blueberry producer in Prince Edward Island, Canada. Fletcher Colpitts inspected their colonies for a winter loss insurance claim last year. Over the winter of 2012-2013 this particular producer lost approximately 700 out of 1000 colonies (70%)! Shrew damage contributed to a large portion of this loss, although not entirely (there were some other management problems). Fletcher said that on average 2 hives out of every pallet of pollinators displayed evidence of shrew predation.
It’s glaringly evident that pygmy shrews pose a large risk to beekeepers (at least in Canada), but there is still good news to be had. It’s very easy to build a modified entrance system to block them from entering your hives. The system has a screen with holes 3/8th’s of an inch. This allows bees to enter without losing pollen from their baskets while also being small enough that pygmy shrews cannot get in. Fletcher has had a 100% success rate with his system and has since kept shrews out of his hives for 30 years.
After researching this topic for nearly a week, there is one thought at the front of my mind: Is shrew damage possible in the northern United States? Some species of pygmy shrew are in the northern US (ME, NH, upper state NY and the Appalachian mountains). It’s just a matter if whether they have learned to seek out honey bees or if perhaps beekeepers have previously mistaken shrew damage for mouse damage. So I ask anyone who may be reading this: Have you seen evidence of shrews in your hives? If so, please share!
When it comes to Varroa control, beekeepers have always been concerned about mites’ resistance to commercial treatments available on the market. It seems the arms race never ends, but changing up treatments throughout the year can help ensure that resistant mites don’t get a foothold. There is a lot of interest in alternative mite control methods, and one that may be a useful addition to the beekeeper’s toolbox is oxalic acid.
Oxalic acid is an organic, naturally occurring compound which can be found in high concentrations in certain plants, notably spinach, rhubarb, and and the aptly named Oxalis. These plants use it as a deterrent against herbivores by making tissues sour and unpalatable (try munching on a raw rhubarb stalk for a demonstration). Oxalic acid is approved for use by beekeepers in Europe, but is still not approved in the U.S. The advantages of using oxalic acid for mite control are as follows: it’s naturally occurring and organic, relatively easy to apply, and is not fat-soluble and therefore does not build up in the wax. The most common method of applying oxalic acid is mixing it with syrup and using a “dribble” technique in the fall or early spring. Mites in sealed brood are not affected, therefore oxalic is not usually used in summer or when there is a significant amount of brood present.
Recently the NorCal Bee Team had the opportunity to assist with a trial of an experimental oxalic acid vaporizer here in NorCal. Oxalic acid clogs normal off-the-shelf foggers, but a local beekeeper/inventor designed a special vaporizer that supposedly does not clog and can save beekeepers time and money when treating for mites. We were called in to assist with the trial by looking at mite levels before and after the fogger was used. The supposed benefits of fogging over dribbling are less ingestion by bees, quicker time to treat (less than 1 minute per hive), and even distribution of acid crystals throughout interior surfaces of the hive. The video below gives an idea of how the fogger is used.
Unfortunately we cannot say if this vaporizer is effective or not because it turned out that there were very few mites to begin with. Another demonstration is being planned so stay tuned!
EFB is often found when nectar flows are sporadic or there is an insufficient number of nurse bees to attend brood. How does EFB spread? European Foulbrood (Melissococcus plutonius) is transmitted when the bacteria become mixed with the bee bread, nectar or diluted honey, and then fed to young larvae. The bacteria then replicate in the larvae mid-gut, killing the larvae within 4-5 days. This causes the larvae to die before sealed in most cases. When the larvae dies it is left in a “stomach-ache” position making it look contorted or twisted in the cell. If the larvae are fed a small amount of the bacteria it may die while sealed or have a decreased lifespan. At this point, EFB looks similar to AFB with scattered sunken cells with perforations. You may also see this if the larvae are fed copious amounts of food to prevent starvation. There are several secondary bacteria associated with EFB. This is often why the disease looks different in many cases depending on how severe the infection is. In hygienic colonies an EFB infection can be mistaken for a failing queen or spotty brood pattern because the bees are removing infected larvae and pupa at a fast rate. This bacterium, like AFB, is very contagious and all equipment should be cleaned once an infection has been found. This bacterium can stay contagious for years but does not produce spores like AFB.
Samples can be taken and sent to the USDA Honey Bee Lab for confirmation of this disease.
• Spotty brood pattern, whitish-yellow to brown larvae, curled upward or twisted.
• Deflated larvae in the bottom of the cell with a defined tracheal system (usually greyish to brown in color with white trachea.)
• Sometimes ropes stretching up to 1.5 cm.
• Odors produced can be sour or fish-like, or no odor at all (different odors can come from secondary bacteria.) Scale is usually from brown to black sunken to the bottom of the cell.
• Outside frames of the brood nest are usually infected first.
The only product labeled for control of EFB is Terramycin (Oxytetracycline hydrochloride). If the colony is infected it is important to treat 3 times with Terramycin 5 to 7 days apart. Re-queening may help by breaking the brood cycle. The shook swarm method and a good nectar flow will also clear up EFB.
For more information and images please visit my older posts HERE.
So what is a virus? A virus is an infectious agent that parasitizes a host cell to replicate. Viruses can cause clinical symptoms, larvae death, or no symptoms at all. BQCV is caused by a virus in the family Dicistroviridae. BQCV is in the genus Cripavirus, which is different from other viruses like Acute Bee Paralysis Virus (ABPV), Israeli Acute Bee Paralysis (IAPV) and Kashmir Bee Virus (KBV) in the genus Aparavirus. Dicistroviruses infect many common insects like ants, bees, flies, leafhoppers, and aphids. The queen production industry is more likely to see this virus (hence its name) but it is still found in smaller operations. Indeed, in most surveys (including the BIP), BQCV is second only to Deformed Wing Virus (DWV), the well-know calling card of varroa. As its name indicates, the BQCV virus primarily attacks developing queens. The virus can still be found in workers and drones, but they do not appear to have any symptoms. This virus is typically detected by PCR, or polymerase chain reaction, a common molecular technique that amplifies the unique genetic signature of the virus.
Queen larvae, when infected, will die and turn a pale yellow color. The larvae will then darken, turning from brown to black. Interestingly, because it is unusual for most pathogens, BQCV kills its host larva at different stages of development, so the remains can be seen at any point after cell capping. Once the larvae are black, you may notice that the outside of the wax queen cells will have a black “oily” spot on them, indicating a dead larva inside. BQCV has been associated with nosema and other viruses, but it is unclear if nosema actually vectors (directly transmits) the virus or if the gut parasite merely takes advantage of an already sickened larva. Varroa infestations have also been linked to BQCV in the workers.
• Larvae/Pupae turn pale yellow with tough skin at first, similar to Sacbrood Virus, but in queen larvae only.
• Larvae/Pupae then darken from brown to black. At this stage the exterior of the cell wall will appear to be dark.
• If one queen cell appears symptomatic, ‘candle’ the remaining cells in the same graft to inspect them for proper development
Unfortunately, as for almost all viruses, there is currently no vaccine or medication for BQCV. The following practices may help hinder the spread of the virus: Sanitation of grafting tools (in ethanol or by flame), control of varroa and nosema, and well-fed Breeder, Starters, Cell builders, and Mother colonies. I have also heard from beekeepers that antibiotics like fumagillin or even Terramycin (oxytetracycline hydrochloride) can clear up BQCV symptoms, possibly because it disrupts the potential interaction with nosema disease.
Chalkbrood (Ascosphaera apis) is typically observed during the spring but symptoms can be seen throughout the year. Chalkbrood contaminates larvae when the spores are mixed with brood food. The fungus will outcompete larvae for food and eventually turn the larvae into a “chalk-like” mummy. The color of chalkbrood ranges from white to grey then starts to turn black-this is when the fungus is producing fruiting bodies. This is the most infectious stage of chalkbrood. The black looking mummies are often what you see outside on the entrance board or in front of the hive. At this point these mummies can spread spores to other colonies in the area. Lack of population may be a contributing factor in the colonies ability to ventilate properly. Proper hive ventilation should prevent chalkbrood.
• Spotty brood pattern.
• Chalk-like mummies at the colony entrance, chalk-like mummies in open brood.
• Early stages of chalkbrood look very similar to SBV but the head is less defined and more round with a sunken appearance.
Apiguard or a thymol based treatment is active against chalkbrood. Vitafeed Green contains thymol and also works against chalkbrood. Beevital Chalkbrood is another product available for treating chalkbrood. Increased ventilation in the hive will help prevent chalkbrood.
SBV or Sacbrood Virus (Morator aetatulas) often appears during spring or colony buildup and causes larval death. The pupa fails to pupate and has a “shrunken head” appearance. When you see perforations in the sealed brood with the infected larvae inside, the perforation is usually choppy or jagged indicating a problem. If the SBV pupa is totally open, the capping has been completely removed by bees and the pupa is most likely greyish-yellow to brown and starting to dry out. When removed the pupa looks similar to a slipper or canoe. Infected adult bees will have decreased life spans. Symptoms:
• Perforated sealed brood, pupa present with undeveloped head.
• Color ranges from pearly white to pale yellow to brown and eventually to black, when it is in scale form it is brittle and easily removed. Treatments:
The only known treatment is to re-queen.
How does AFB spread? American Foulbrood (Paenibacillus larvae) is introduced to the hive by drifting bees from nearby colonies, infected equipment/tools, beekeepers and robbing. The infection begins when spores enter the hive, and then food contaminated by spores is fed to the larvae by nurse bees. Once spores are in the midgut the bacteria take over using the larvae as a source of nourishment. After the cells are sealed, death occurs. If death occurs while in the pupal stage, there may be a protruding tongue present. When there is a serious infection you can notice moisture on sealed brood as they start to sink. Sunken sealed cells are a result of decomposing larvae. AFB is very contagious and all equipment must be cleaned before using it in healthy hives.
The AFB scale is very hard for the bees to remove and can infect colonies for years to come. This is why some states have a “burn only” policy, but others allow the use of antibiotics to control the disease. It is important to have the AFB tested by a lab (USDA Honey Bee Lab) to identify if the AFB strain is resistant to Terramycin (oxytetracycline hydrochloride).
• Spotty brood pattern, perforated sealed brood with coffee brown larvae inside, sunken sealed brood, coffee brown larvae sunken to the bottom of the cell.
• Moisture on sunken sealed brood, protruding pupal tongue (rare), and rotting smell (compared to rotting meat or sulfurous chicken house).
• Light to dark brown to black scale that is hard to remove.
• Often colonies next to infected colonies will show symptoms of the disease.
• Larvae rope at least 2 cm.
It is best to burn all colonies infected with AFB but you can treat infected colonies with antibiotics. There are two antibiotic treatments for AFB: Terramycin and Tylan. If AFB is not resistant to Terramycin (oxytetracycline hydrochloride) then this antibiotic is used. If the strain of AFB is resistant to Terramycin, than Tylosine is the antibiotic used to treat the colony. Treating colonies 8 weeks prior to the nectar flow is recommended to prevent honey from being contaminated.
Note: Tylan is supposed to be used once symptoms occur in the hive because it leaves behind residuals for far longer than Terramycin. Terramycin is the only antibiotic that can be legally used prophylactically.
PMS or Parasitic Mite Syndrome is a condition that causes a honey bee colony to deteriorate and eventually dwindle away and die. There has not yet been a pathogen detected which causes the brood symptoms that appear with this syndrome. However there are always varroa mites present with this syndrome. The brood symptoms look similar to other diseases but the larvae don’t rope. Colonies with PMS will show symptoms of white larvae that are chewed or pecked down by workers. Larvae may appear sunken to the side of the cell and may show symptoms of white with some debris at the posterior end. Pupa will be chewed down/removed or the pupa face chewed part of the way down as seen in the photo. Most of the symptoms shown are from hygienic bees trying to remove varroa mite infested cells and or larvae/pupa from cells. There is sometimes color to the larvae and this is attributed to age, decomposition or secondary bacteria.
• Spotty brood pattern, varroa mites present on adult bees.
• Mites can often be seen crawling across sealed brood.
• Mites can also be found in open brood cells (usually chewed down larvae, refer to images)
• Lack of adult population (time-dependent).
• Large colonies are aggravated by high varroa mite levels and often show increased aggressiveness, lack of eggs and developing larvae (due to unfit conditions for raising brood), supercedure cells are often present, crawling bees near hive entrance or bees with DWV (Deformed wing virus).
• No odor present until the chewed down larvae start to change color and decay.