Sacbrood Disease Treatment and Management for Honey Bees

Quick Overview

Sacbrood disease, caused by the Sacbrood virus (SBV), is a viral infection that affects honey bee brood, leading to the death of larvae. The disease is transmitted through various means, including robbing, drifting bees, and beekeeping practices. While adult bees can carry the virus without showing symptoms, infected larvae fail to pupate and die, exhibiting a rounded shape and color changes from white to yellow, then brown, gray, and eventually black.

This article emphasizes the importance of diagnosing Sacbrood through symptoms, field tests, and laboratory techniques. Key symptoms include changes in the shape and color of larvae, distinct two-tone coloration, and the posture of dead larvae with raised heads. The disease can be confused with American Foulbrood due to similar symptoms, such as perforated cappings and the presence of scales, but there are notable differences in the larvae’s appearance and the ease of removing the scales.

There is no chemical cure for Sacbrood, so management focuses on prevention and mitigating stress on the colony. Practices like requeening with genetically superior stock, enhancing hive hygiene, and maintaining strong colonies are recommended. Requeening interrupts the brood cycle and introduces hygienic behavior, which can help control the disease. Additionally, apiary management techniques such as spacing hives, feeding stressed colonies, and merging weakened colonies can bolster colony strength against Sacbrood.

Vigilance in early disease identification, regular inspections, and the importance of hygiene in preventing disease transmission. I advise beekeepers to clean tools and equipment and to be cautious when transporting bees to prevent the spread of Sacbrood.

Though Sacbrood disease poses a significant threat to honey bee larvae, with careful management and preventive practices, beekeepers can control its impact and maintain healthy colonies.

About Sacbrood Disease

Sacbrood disease is a condition that affects honey bee brood. The disease causes the death of afflicted honey bee larvae. Any honey bee larvae that have the disease do not pupate. Adult honey bees can be affected by the disease too, but does not show any characteristic symptom. Even then, the lifespan of the afflicted adult bee is significantly reduced.

Sacbrood disease in honey bees is caused by a virus called the Sacbrood virus (SBV). So far, research has found more than one genotype of this virus. This article helps you understand the disease better and also takes you through treatment and management for honey bees.

What Causes the Sacbrood Disease?

The Sacbrood disease is caused by the Sacbrood virus. It comes into the beehive through wandering bees, robbing, and the beekeeper transferring it from an infected hive, among other avenues. There are various practices you can employ that will help prevent the entry of the Sacbrood virus into the beehive. One such method is replacing your Queen bee.

How it Spreads

The Sacbrood virus can remain viable in honey bee larvae for up to a month. Swarming has spread the disease to nearly all beekeeping regions of the world. As such, it has become a significant disease in the USA. Varroa mites also contribute to the spread of this disease. Nurse bees infected by the virus are the biggest culprits in the spreading of it throughout the hive. Nurse bees pick up the virus from living infected larvae or remains of dead bee brood in the colony. They then transmit it to other larvae when feeding them.

Adult bees infected by Sacbrood disease are asymptomatic. They however exhibit behavioral changes and have a short lifespan. Worker bees that have Sacbrood disease start going foraging early in their lifecycle and then stop soon after. They do not go out of the beehive to collect pollen, nectar, or water. Even then, any pollen in the beehive can be infected by the virus which causes Sacbrood disease in the young bees that feed on it.

Symptoms of Sacbrood Disease

Diagnosis of honey bee diseases is important for their management. You can use various symptoms and signs in the beehive to diagnose honey bee diseases. Laboratory results are also available to beekeepers. Diagnosis of honey bee diseases such as Sacbrood using symptoms, field tests, and laboratory techniques is more reliable than diagnosis based on symptoms only. Various aspects of the beehive, honey bee colony health, honeycomb, and bee brood are evaluated in diagnosing Sacbrood disease.

You should inspect the face of the brood comb with attention paid to the state of brood cells. The brood cells that have their honey bee larvae infected by Sacbrood viruses can be capped or uncapped. When capped cells have Sacbrood, perforations might be present in the capping. They are visible on close examination of the cell capping. Presentation of Sacbrood can be confused with another disease of honey bees called American Foulbrood Disease (AFB). This is because the perforations are usually made by honey bees that have detected dead larvae underneath the capping. They do this in an attempt to remove the dead larvae from the cells. Some bees succeed while others do not.

This activity by the adult bees results in the spread of the Sacbrood disease in the beehive. The bee cleaning out the cell comes into contact with the Sacbrood viruses from the dead brood and transmits them to a healthy brood if it feeds or comes into contact with them.

At the same time, this hygienic behavior of honey bees can help curb infections if it is done at a large enough scale. It removes the reservoirs of infectious agents from the beehive. The Sacbrood infection can then persist at low incidence in the beehive.

The symptoms of Sacbrood disease to look out for include:

1. Shape of Dead Honey Bee Larvae

Honey bee larvae that are killed by Sacbrood virus infection die in brood cells. In most cases, the larvae with Sacbrood disease die before they can pupate. On inspection, the larvae are found to have remained in a rounded shape. The larvae killed by most other bee brood diseases do not usually retain their rounded shape. This is especially true in the early stages of dead honey bee larvae decomposition from diseases. Skins of the larvae with Sacbrood infection become tough and quite plastic-like. The skins retain segmentation that is visible in living honey bee larvae. In American Foulbrood infections, on the other hand, segmentation disappears in a dead honey bee brood.

2. Dead Brood Color Changes

Color changes in dead brood from Sacbrood infections are observable and can be used in the diagnosis of the disease. The dead brood transitions from pearly white to brown through yellow. After it turns brown, the larvae then take on a gray color. After the gray color, the dead bee brood turns black. These transitions can be seen on the face of brood comb from areas of early infection to areas of recent infection.

In using color to diagnose Sacbrood disease, differences with the American Foulbrood disease color changes are exploited. In American Foulbrood disease, the dead honey bee brood moves through a light coffee brown color to darker coffee brown shades until it turns black. The grayish color stage is not seen in American Foulbrood infections.

3. Posture and Coloration

The posture and coloration of the bee brood that has died from Sacbrood disease is distinct. A darker shade of color is found on the heads of honey bee larvae that die from Sacbrood disease. The rest of the body of the bee larvae has a lighter shade of color than the head. Additionally, the posture of the head of dead larvae is raised. This is different from honey bee larvae that die from American Foulbrood infections.

Honey bee larvae infected by Sacbrood disease turn in their brood cell and die with the head facing up. In the brood that dies from American Foul Brood disease, two-tone coloration is not observed. The larvae take on one color with a uniform spread over the whole body. Additionally, the head of dead brood in American Foulbrood infections is not raised.

4. Sacbrood Bee Brood Scale Inspection

Sacbrood infection of honey bee larvae causes bees to remove dead larvae from brood cells. If the larvae are not removed, it dries down and turns into a black scale eventually. The scale remains in the cell and can be confused with the remnants of brood that have died from other bee diseases. The scale remnant of larvae that have died from Sacbrood honey bee disease is easily removed from the cell in one piece.

This is unlike in other honey bee diseases such as American Foulbrood, where the scale is firmly attached to the cell walls in the brood comb and cannot be easily removed in one whole piece. Honey bee brood that has died from Sacbrood disease and turned into a scale is difficult to find in the beehive. It is only found in a large spread of the disease through a lot of the bee brood in the beehive. Such massive infections of Sacbrood disease are not common in beekeeping.

5. Puncturing Dead Bee Brood

Dead larvae in Sacbrood infections can be removed from the cell it occupies in its early stages of decomposition. The larvae are easily pulled from the cell using a matchstick or twig. They hang from the matchstick in a sac-like fashion. This is the behavior of the dead brood that gives this disease its name. Further symptomatic diagnosis of the brood is done by puncturing it. If the cause of death is truly Sacbrood disease, the contents of the bee larvae sac are found to be watery and they easily flow out of the larvae skin.

Ropiness Test for Sacbrood Disease Diagnosis

Brood death in a beehive can be a result of many varying causes, not limited to a specific disease. In the event that a beekeeper finds dead brood in their beehives, the Ropiness test is often applied. When dealing with a case of Sacbrood disease in the beehive, the Ropiness test can be applied but does not give clear results. It is not reliable in the case of Sacbrood diagnosis. This is a result of a honey bee brood that has died from Sacbrood infection, undergoing ecdysis and liquefying into a non-sticky goo. The fluid left after the larvae are dead does not easily form a rope in the Ropiness test. If ropiness is found in a Sacbrood infection, it is usually a result of the activity of opportunistic bacteria on the dead larvae.

Ropiness is seen as a result of many honey bee diseases including American and European Foulbrood Disease. After conducting the Ropiness test, you should interpret its results taking into consideration other symptoms and signs observed in the beehive.

If you cannot make a final decision about the disease you are facing after conducting the Ropiness test, seek the services of a laboratory to help you with the identification of the disease. You can use easily available materials to take a sample from the beehive. Follow best practices when collecting the sample and sending it to the laboratory for processing.

Can you Cure the Sacbrood Disease?

Chemical control of bee diseases is a preferred option by beekeepers where it is available. With Sacbrood disease, however, there is not much the beekeeper can do using chemicals to control the disease. There is no cure for it. Management and treatment of the disease are therefore largely done by preventive and pressure relief practices. In the apiary, the pressure caused by the Sacbrood disease can be eased to make the affected honey bee colony stronger, and able to withstand other management practices carried out to keep the disease at bay. Requeening the honey bee colony is a very reliable hive management practice that helps with the control of Sacbrood disease.

In addition to bringing in a fresh queen bee into the honey bee colony, practicing good hygiene at the apiary is important for disease prevention. Sacbrood disease establishes itself with greater ease in beehives that are not very clean. Hive hygiene in modern beekeeping is a net product of the efforts by both the beekeeper and the honey bee colony. Broken comb, spills, dead bees, etc., should be removed from the beehive when you see them. Honey bees clean the beehive but may take too much time to remove large pieces of debris. Helping them with those allows the bees to focus their hive hygiene efforts on areas in which they perform best.

A beehive in which Sacbrood disease has taken root may be saved by assistance in hive hygiene given by you. The bees saved from dealing with debris and dead comrades shift to clearing dead infectious larvae from brood comb cells. To facilitate greater beehive hygiene, you may install a screened bottom board in the infected beehive. The screened bottom board allows dead bees and larvae through it and onto the ground. You can then sweep up the debris and dirt from under the beehive.

Apiary Management for Sacbrood Disease Treatment in Honeybees

Other apiary and beehive management practices you can use to curb Sacbrood disease in your apiary are spacing of hives to prevent honey bee drifting, feeding to ease pressure on infected honey bee colonies, and merging weakened honey bee colonies. Strong honey bee colonies are not easily overwhelmed by Sacbrood disease.

1. Hygienic Honey Bee Colony Behavior

Hygienic behavior in bees is heavily influenced by their genetics. This is used in favor of the beekeeper to control Sacbrood disease. A honey bee colony that is affected by the disease is an indicator of poor genetics. You are encouraged to find a queen bee of better stock and bring her into the beehive. It causes some disruption in the beehive yes, but improves the overall genetics of the honey bee colony.

Eventually, all worker bees in the beehive are offspring of the new queen bee and they improve hygiene in the beehive. When requeening, be sure to use a queen of better stock than the one you already have in the honey bee colony infected by Sacbrood disease. You can ask fellow beekeepers near you to give or sell one to you.

When requeening a honey bee colony because of a Sacbrood infection, feeding the colony helps relieve some of the stress the colony experiences. It takes some time before the new queen bee is released from her cage and starts laying eggs. The disruption in the brood cycle caused by this is also believed to contribute to better management and eventual Sacbrood disease treatment in honey bees.

2. Requeening for Sacbrood Disease Treatment

Honey bees can control Sacbrood virus infections through hygienic behavior and the ability to detect dead larvae under brood cell capping and remove them. Stresses exerted on the honey bee colony can however cause it to be overwhelmed by the infection.

Nectar and pollen shortages, a poorly performing queen, and climatic conditions reduce colony strength and the ability of the colony to fight Sacbrood disease. Infestations by pests and other diseases of honeybees can also contribute to lowering colony strength. If you find such conditions in your beehives, take measures to bring the colony back to its proper population. More worker bees should be added to the colony. Methods of triggering the production of more worker bees include providing sugar and pollen to the honey bee colony.

Beekeepers with more than one beehive of the same configuration can bring in additional frames of bee brood. When the brood finishes development and emerges as adult bees, it contributes to the increase of the adult bee population in the honey bee colony. The frame added to the beehive can replace an infected brood frame in the beehive afflicted by Sacbrood disease, or put in the super box immediately above the brood box of the beehive.

Placing the brood frame in the super box requires you to remove the queen excluder if there is one in your beehive. It allows the queen bee to move to the area in which you have placed the brood frame. She brings with her many nurse bees. These nurse bees get to know there is more brood in the beehive and will begin to feed them. Additional space for the queen to lay eggs can also save the beehive from total collapse.

How to Requeen a Beehive for Sacbrood Disease Treatment in Honeybees

To requeen a beehive, bring in a new queen bee in a queen cage with a candy plug. Remove the covers over the candy plugs and suspend the queen bee in the beehive. A central area in the beehive allows bees in the colony to get the queen’s pheromones in even distribution. Honey bees chew through the candy plug to free the queen bee from her cage.

Depriving the colony of honey and sugar feed helps speed up the rate at which they free the queen from the cage. Honey-bearing frames should be returned to the beehive once the queen bee is free of her cage. Feeding should also be instituted to help the colony get the best nutrition.

After bringing in a new queen bee, look out for queen cells in the beehive and remove them, or destroy them. It helps the new queen bee not have to deal with competition while the honey bee colony is stressed by the Sacbrood disease affecting it.

3. Vigilance for Early Sacbrood Disease Identification

Regular inspection for signs of disease helps you avoid incidences of Sacbrood disease in your apiary. Requeening should be done if you find that more than 5% of the brood in a honey bee colony is affected by the disease.

Sacbrood-infected comb in the beehive should be removed and melted down or placed in storage for a period of not less than 2 months. The Sacbrood virus is short-lived when it is not being transmitted between larvae in a honey bee colony.

A combination of infected frame removal and requeening, allows the new queen bee to replace the brood in the beehive with her brood. As a disease management precaution, I advise beekeepers to cycle out their brood frames every 2-3 years. You can do this gradually in the beehive or wait and replace the entire comb at once.

Preventing Transmission of Sacbrood Disease

Tools and equipment for apiary management should be cleaned before use in different beehives. In your apiary management, get into the habit of washing tools and equipment with solutions that can kill infectious agents that might be on the surfaces. Washing soda and bleach solutions are great for beekeepers to use to sanitize their tools and equipment.

A clean cloth wetted using the solution can also be used for wiping down the tools and equipment. Scorching can also be used on the tools and equipment that can withstand it. Where the beekeeper must use beehive parts from one beehive in another, adequate cleaning should be carried out on the beehive parts before use in the next beehive. This prevents the parts of your beehive from moving infectious agents from one beehive to another.

It is important to note that a disease such as Sacbrood disease can be in a honey bee colony at low levels such that it does not affect the colony. Upon transfer of the infectious agent to another honey bee colony, it may cause a lot of problems in the second colony. The difference is usually because of colony strength and recent changes in the beehive such as requeening. Even when a beehive seems to be all good, the parts from it should be cleaned before use in another beehive.

Care should be taken when transporting bees and using them for pollination services. It is important not to let up on your observance of hive hygiene. During transit, do not allow hygiene standards to fall. After arrival at your destination, continued hive management should include your usual hygiene improvement practices so that the chances of diseases infecting your bees remain low.

Conclusion

Honey bee larvae with Sacbrood virus die because they fail to pupate. The ecdysial fluid from the death and decomposition of the larvae accumulates under the skin. It forms a sac after which the disease is named. The infected larvae change in color and dry out into a scale. This viral disease of honey bees has shown greater prevalence in spring to the early weeks of summer. It requires you to be very vigilant about it, so it does not cause you losses in your beekeeping operation. Successful management of the disease is possible.

You should also put in place measures to prevent the occurrence of the disease in your honey bee colonies. Draw from the given management solutions to safely carry out Sacbrood disease management and treatment in honey bees.

References

• https://beeinformed.org/2013/10/29/sacbrood-virus-sbv/ 
• https://www.daf.qld.gov.au/business-priorities/biosecurity/animal-biosecurity-welfare/animal-health-pests-diseases/beekeeping-in-queensland/diseases-and-pests/sacbrood 
• https://nationalbeeunit.com/index.cfm?sectionid=69 
• https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/sacbrood-virus
• http://www.dave-cushman.net/bee/sacbrood.html

Has your beehives ever been afflicted by the sacbrood disease? Leave a comment below and let us know what your experience was like.