Varroa Mites

Two varroa mites feeding on a honeybee larvae
Varroa Mite Classification
Class: Arachnida
Order: Mesostigmata
Family: Varroidae
Genus: Varroa
Species: Varroa destructor

Varroa mites, also known as Varroa destructor, are parasites that feed on honeybees, including Apis cerana and Apis mellifera

Varroa destructor (Varroa mite) is a species belonging to the genus Varroa in the family Varroidae. They belong to the order Mesostigmata, which is part of the class Arachnida.[1]

The Varroa mite is named after Marcus Terentius Varro, a Roman beekeeper. Their species name, destructor, derives from the destructive impact of the Varroa mite on honey bee colonies.

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    Where Can Varroa Mites Be Found?

    The Varroa mite is found in every major honey-producing country except Australia, including China, Turkey, and Iran, the top three honey producers in the world.[2] 

    Varroa mites have never been eradicated from any country in which they are found [3]

    What Does a Varroa Mite Look Like?

    Varroa mites are tiny, oval-shaped arachnids with eight legs. Female Varroa mites are reddish-brown in color, while males are bright white.

    The Varroa mite measures approximately one millimeter in length and up to two millimeters in width. Compared to adults, juvenile Varroa mites are smaller and have a lighter brown color. Varroa mites do not have eyes.

    As a result of feeding on the haemolymph of honeybee larvae, Varroa mites may transmit viruses to them. Consequently, this will have an adverse effect on the development of the larvae into adult honeybees.

    It is possible to mistake Tropilaelaps mites for Varroa mites due to their similar appearance. However, they are much smaller than Varroa mites, measuring only one millimeter in length and up to one millimeter in width.

    There are also pollen mites that look somewhat similar to Varroa mites, but they are harmless. As opposed to Varroa mites, these mites are lighter in color and much smaller, measuring no more than half a millimeter in both length and width. 

    Where Do Varroa Mites Live?

    The Varroa mite lives primarily in honey bee hives. The Varroa mite lays its eggs within the brood cells of bees and develops and mates within them. 

    Varroa mites may sometimes be found on the bodies of adult honey bees, but young mites and male mites feed and live only on the larvae and pupae. 

    The young female Varroa mites hatch alongside the bees since the adult female Varroa mites lay their eggs within the brood cells themselves.

    Once the bee breaks open the beeswax cap and crawls out, Varroa mites emerge from the cell. Since the male mites die shortly after mating, they never leave the brood cells.

    Why Are Varroa Mites Dangerous to a Honey Bee Colony?

    Varroa mite infestations cause worker bees to live shorter lives than those that are not infected, thus making these mites dangerous to honey bee colonies. Generally, bees infected with Varroa mites survive to adulthood. 

    Varroa mites feed on the haemolymph of bees, which is similar to bee blood. By eating this haemolymph, Varroa mites reduce the bee’s ability to grow, which means that once hatched, it will be lighter and smaller than a healthy bee.

     In addition, bees infested with Varroa mites have difficulty navigating and return to the hive less frequently. In essence, bees infested with Varroa mites are more likely to become lost in the world than healthy bees.

    Transmission of viruses is another way in which Varroa mites pose a threat to honey bees. Varroa mites can transmit many viruses, including the deformed wing virus, which results in shriveled or small wings on bees as well as an inability to fly. 

    What Is Varroosis?

    Varroosis is the name for the condition that occurs when Varroa mites infest a colony of bees. The term is primarily used to describe the virus and damage caused by Varroa mites within a colony of honeybees.

    Why Do Varroa Mites Attack Honey Bees?

    Varroa mites are obligate parasites of honey bees. Although it is unknown why the Varroa mite prefers honey bees as its host, parasites are significant for biodiversity and affect the competitive outcomes of hosts.

    Varroa mites attach themselves to the body of the bee and weaken it by sucking fat from the body. Female Varroa mites feed on the haemolymph of adult honey bees, larvae, and pupae, reducing the bee’s growth capacity.

    Varroa mites are capable of reproducing only on honeybee brood, and their entire life cycle relies on exploiting honeybee hives. 

    The Varroa mite prefers nurse bees (worker bees) over older and younger bees. Nurses provide the best reproductive conditions for Varroa mites.

    Do Varroa Mites Only Attack Honey Bees or Other Insects Too?

    Since the Varroa mite feeds exclusively on honey bee haemolymph, it does not feed on any other insects or animals. Varroa mites can only live within a honey bee colony.

    Even if the Varroa mite is transferred from a honey bee to another insect, it will die as it will not have a honey bee colony to live in. The entire life cycle of the Varroa mite takes place within a honey bee colony.

    What Does a Varroa Mite Do to a Honey Bee's Body?

    The presence of Varroa mites negatively affects the growth and navigational capabilities of honey bees. As part of this process, Varroa mites feed on the larvae and pupae of bees, eating their haemolymph.

    Furthermore, Varroa mites transmit viruses to bees, causing deformed wings or thoraxes and generally unhealthy bees with a shorter lifespan. As a result, honey bee colonies find it very difficult to carry out their daily activities and survive when infested by Varroa mites. 

    What Is a Varroa Mite Infestation, and What Can It Lead To?

    Varroa mite infestations begin when adult female Varroa mites move between bees of different colonies. Varroa mites jump from one bee to another, accompanying the bee back to the colony and laying eggs there.

    Varroa mite infestations are easily caused when bees fly close together, which is similar to how dogs transmit fleas among themselves. 

    Female honey bee infected with Vorroa Mite on its back
    While bees infested with Varroa mites may survive to adulthood, they will have difficulty carrying out their daily activities, thereby limiting the growth of the colony and the bees themselves.

    Infestations caused by Varroa mites are almost impossible to eradicate or prevent, which means that the majority of infestations are essentially permanent. It is possible, however, to limit the population of Varroa mites within the colony in order to control the damage they cause. 

    An infestation of Varroa mites can result in a number of negative effects on bee colonies, including death, deformation, and smaller body sizes. Varroa mite infestations simply make it more difficult for bees to survive and carry out their daily tasks.

    How to Detect a Varroa Mite Infestation

    Varroa mite infestations can be detected in several ways, depending on how much brood is present in the hive.

    When the hive has a large number of larval and pupal bees, most of the Varroa mites will be living in the brood cells with them. However, if there is no brood in the hive, adult female Varroa mites will only live on the bodies of adult bees. 

    The following sections cover the three main ways to detect Varroa mite infestations. 

    Alcohol Washing

    If there is not a great deal of brood in the hive, alcohol washing may be a suitable technique to use. This is because it tests the adult bees for adult female Varroa mites that are resting on them. A jar and rubbing alcohol are all that is required for this technique. 

    It should be noted, however, that this method does kill the bees being tested; therefore, it could result in the loss of approximately 300 bees. 

    In order to perform this method, beekeepers must fill a jar halfway with rubbing alcohol and then add half a cup of calmed bees. After shaking the jar for about 20 seconds, any Varroa mites that may be present should be dislodged. 

    The lid is removed and the rubbing alcohol is poured out of the jar using a sieve while holding the bees’ bodies back. 

    Since the Varroa mites are so small, they will pass through the sieve without difficulty, while the bees will remain in the jar. Then, the mites can be counted to determine the level of infestation in the hive. 

    Sugar Shaking

    Sugar shaking is most effective at times of low brood levels, since it tests for Varroa mites on the adult bees themselves. Confectioners’ sugar and a cup are all that is required for this method. This method of testing for Varroa mites will not kill any bees. 

    Similarly to the alcohol method, this method involves shaking approximately half a cup of bees in a jar with a tablespoon of confectioner’s sugar. 

    This method requires the top of the jar to be perforated with 3-5 millimeter holes in order to allow the sugar to be shaken out at the end. 

    Approximately five minutes after the bees have been shaken in the sugar, the sugar is poured into a container of water. Varroa mites will float on the surface of the water as the sugar dissolves in the water, making them easy to count. 

    Drone Uncapping

    Vorroa mites on bee pupae

    In instances where bees are brooding at high levels, drone uncapping is a very effective technique. Instead of testing adult bees for Varroa mites, drone uncapping tests larvae and pupae for the parasite. 

    In this method, at least three brood frames are removed from the hive and uncapped using a cappings scratcher, resulting in the larvae and pupae being removed. 

    Next, the larvae and pupae are examined for Varroa mites, which can easily be seen due to their white color. 

    The brood of drones that is tested is killed using this method.

    How to Prevent and Get Rid of Varroa Mites

    The first step in preventing and eradicating Varroa mites is to determine whether the mites are present, and if they are, how many of them there are. 

    Breeding bees with built-up resistance to Varroa mites is the most effective means of preventing their infestation. However, there are other ways to reduce Varroa mite populations in colonies that are not resistant to the mite.

    Chemicals

    Varroa mites can be controlled using a variety of chemicals or miticides. The majority of these chemicals come in the form of strips coated with miticides or gels.

    using chemicals to treat bee hive infested with Vorroa mites
    Due to the rapid growth of Varroa mites, the introduction of just a few can severely damage a colony. Therefore, it is imperative that Varroa mites be removed as soon as possible.

    Apiguard is an excellent option if a natural chemical is desired as it is made from thyme plants and is safer for bees and humans than other chemicals.[4]

    Comb Trapping

    In order to perform comb tapping, a special drone comb is purchased, which is imprinted with large hexagons. As the bees will only lay drone broods on this comb, most of the Varroa mites in the colony will congregate in these brood cells. 

    Once the drone brood has been laid in these cells and the Varroa mites have been isolated, the drone comb can be removed and frozen overnight.

    In spite of the fact that this will kill the drone brood in the comb, most colonies produce far more drones than they require. Therefore, there is no significant damage to the colony. 

    Once the comb has been frozen and the Varroa mites and bees have been killed, the drone comb is returned to the hive and cleaned out and reused by the nurse bees (worker bees).

    Sugar Dusting

    Sugar dusting is carried out by dusting the bees with powdered confectioner’s sugar in an effort to remove Varroa mites from their bodies. 

    A beehive is smoked, the combs are removed one at a time, and confectioners’ sugar is sprinkled over them. For minimizing damage to the larvae, one should only dust closed brood cells and adult bees and not open brood cells. 

    By using this method, the Varroa mites will drop off the bees’ bodies. In these circumstances, the majority of Varroa mites will be on the bodies of the bees, making it an excellent method to use when the bees do not have large amounts of brood.

    How Do Varroa Mites Spread Between Apiaries & Colonies?

    Female Varroa mites spread by climbing on the thoraces of bees and being carried along with them while foraging. Bees from one colony transfer Varroa mites to bees from another colony when they are close to one another. 

    Once the female Varroa mite has been attached to the bee from the new colony, it is carried back to the hive. In the hive the Varroa mite lays its eggs in the brood cells. 

    Reproduction & Lifecycle of Varroa Mites

    Adult female Varroa mites lay their eggs on the bottom and sides of honey bee brood cells. In addition, female Varroa mites may also lay their eggs directly on the larvae and eggs of honey bees.

    As drone larvae have a longer brood cycle, female Varroa mites prefer to lay eggs on them. Varroa mites enter the brood cells while they are still open, and lay their eggs after beeswax has been applied. 

    The first egg that is laid by the Varroa mites is always a male egg, whereas the rest are female eggs. Upon hatching, the eggs of the Varroa mite undergo two stages of development. 

    Initially, they are protonymphs (newly hatched form of Varroa mite) and then they become deutonymphs (Second larval form occurring in the development of Varroa mites).

    Diagram showing the lifecycle of Vorroa mites
    The importance of preventing Varroa mite infection cannot be overstated, as once a colony is infected, it is very difficult to eradicate the mites, often resulting in the loss of the colony.

    The development of female Varroa mites can take up to a week, while that of males takes roughly five days. 

    As soon as the Varroa mites reach adulthood, the male mates with the female within the brood cell and dies. Varroa mites emerge from their cells together with the honey bee when the honey bee they are living in emerges as an adult. 

    The lifespan of an adult female Varroa mite is typically two months. As soon as the female Varroa mite becomes an adult and mates, it lays eggs, thereby resuming the life cycle.

    Varroa Mite Population Growth

    What does a Vorroa Mite look like

    The population of Varroa mites is closely related to the climate in which the host bees live. The Varroa mite population often decreases during the winter in colder climates due to bees overwintering and not making larvae all year long.

    Meanwhile, in warmer climates where bee broods are present all year round, the Varroa mite population remains relatively stable. 

    Varroa mite populations are also affected by the amount of drone brood in the hive. There will be a decline in the Varroa mite population if a small number of drones are laid. This is because Varroa mites prefer to lay their eggs in drone brood cells rather than in worker brood cells. 

    Due to drone larvae developing at a slower rate than worker larvae, Varroa mites receive more time to develop with the bees. 

    Because of the exponential growth of the Varroa mite population, the introduction of just a few can cause serious damage to a colony. 

    In the course of the life cycle of the Varroa mite, more and more female mites are produced. A colony of Varroa mites may contain a few mites at first, but eventually they may number in the thousands.

    Sources

    [1] Wikipedia [2] Statista [3] Bee Aware [4] Dummies

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