Module 8: Diseases, Viruses and Predators of Honeybees

Table of Contents

Honey Bee Health

Bees are under attack from a number of treats. In this module we will identify threats that our specific to our region, but also touch briefly on emerging threats that exist globally.

Chalkbrood

Chalkbrood is caused by the fungus Ascosphaera apis. Infected brood turns hard and white, resembling a piece of chalk. Fruiting bodies make the mummies develop brown or black coloration. Chalkbrood mummies can be observed in the brood cells, on the bottom board, or on the ground in front of the hive. Chalkbrood can be managed by requeening and ensuring colonies are strong and housed in dry hives.

Colonies with good hygiene will try to remove the mummy larva — it is called chalkbrood because the mummies are chalk like in appearance and touch.  These mummies can often be seen at the entrance of the hive.

There is no chemical approved treatment for this disease.  The best management plan would be to: strengthen a weak hive with more brood and bees, replace the queen (literature indicates that it might be genetic characteristic) with a queen of known hygienic behavior.   

To avoid spreading chalkbrood, you can avoid using pollen from a chalkbrood hive for supplemental feeding and avoid mixing frames of comb from a chalkbrood hive with other hives you may have.

Varroa Destructor

There are two species of Varroa mites: Varroa jacobsoni and Varroa destructor. The two species differ slightly in appearance and can be differentiated by the naked eye: Varroa destructor is larger and more ovular (less circular) in shape than Varroa jacobsoni

Both of these species parasitize the Asian honey bee, Apis cerana, and have likely done so for hundreds, if not thousands, of years. During this time, the mites have co-evolved with the Asian honey bee and therefore do not pose a significant threat to colony health. 

In the 1960s, however, one of the two mite species, Varroa destructor, switched hosts to parasitize Apis mellifera, when colonies of those Western honey bees were moved into an area in Asia where Asian honey bees resided. (Varroa jacobsoni did not switch, and are unable to reproduce in Western honey bee colonies.) Varroa destructor has since spread across the globe through natural migration (swarming) and commercial transportation.

Varroa Destructor can be the host for a number of deadly viruses that can harm your bees:

  • Deformed Wing Virus (DWV) Type A,B
  • Kashmir Bee Virus (KBV)
  • Acute Bee Paralysis (ABP)
  • Israeli Acute Paralysis Virus (IAPV)
  • Slow Bee Paralysis virus (SBPV)
  • Parasitic Mite Syndrome (PMS)
  • Kakugo Virus.

 

There three key ways to detect Varroa Mite

  1. Screen bottom boards and a sticky board.
  2. Second method involves checking drone brood for mites.
  3. third method  involves scooping up 100 or so bees and subjecting them to a alcohol roll test.

 

The are a number of products available on the market, we have listed some of the more popular and safe treatments below:

  • Aluen CAP – Oxalic Acid slow release strips
  • Apiguard
  • Api LIfe Var
  • MIteAway Quick Strips
  • Oxalic Acid crystals
  • Hop Guard
  • Apivar

 

The treatments Apistan® and CheckMite+® are not included in this list because we do not recommend beekeepers use them. They remain in wax for years and mites have developed resistance. There have also been cases of resistance to Apivar®.

It is important to rotate treatments, remove treatment strips promptly, and practice Integrated Pest Management to reduce the likelihood of resistance developing to any treatment. Make sure you monitor after the treatment is finished (or regularly every month) to determine efficacy.

Wax Moth

There are two general types of wax moth: Galleria mellonella L. the Greater Wax Moth and Achroia grisella F. the Lesser Wax Moth. Both do considerable damage to bee hives that are in weak condition and to stored comb in supers. It is the Wax worms are a serious problem in warm weather and dark conditions. They can do a lot of damage in a very short period of time. Wax moths attack weak hives.  Strong hives will kept them under control.  

Wax moths do not like light.  Exposing equipment to light, closing up equipment tightly and fumigating with “Para-moth” (Para-Dichlorobenzene crystals) a product available from most bee suppliers, and using biological control such as B401 Certan (Bacillus thuringiensis). Or you can freeze the affected frame for 2 days.

Tracheal Mites

The tracheal mite, Acarapis woodi, is a very small, white mite that measures about 150 micrometers in length (a micrometer is one thousandth of a millimeter). Their effect on honey bees is referred to as “Acarine disease.” They infest adult honey bees of all castes and do not affect brood. 

They reside exclusively in the prothoracic trachea–the tracheae located at the very front of the thorax, just at the honey bee’s “neck.” To get to these tracheae, they crawl through the spiracle at the base of the wing of 1–2 day old adult bees, usually during the night when colony activity is low. After a few days in the tracheae, they begin to reproduce, laying eggs that will develop into adults. 

Their offspring mate with each other and mature inside the trachea. Tracheal mites only infest young bees, identifying them based on their odor. This allows the mites to complete their entire life cycle before the adult bee dies. Before the bee dies, the tracheal mites exit this bee’s body through its spiracle and looks for other young bees to infest.

Drifting bees between hives, and swarms produced from infested colonies are ways mites are naturally spread within an apiary and between apiaries. Mites are spread within a colony by bee contact. Mature female mites exit the bee trachea and climb to the tip of a body hair. Upon contact with a newly emerged bee, the mite transfers to the hairs of the new host and enters the trachea where it will complete it life cycle. If the mite fails to locate a new host within 24 hours, it will die.

No one symptom characterizes a tracheal mite infested colony. Tracheal mites are believed to shorten the life span of adult bees, affect flight activity, and result in a large number of crawling bees that are unable to fly. The wings of mite infested bees are often disjointed with the hind wing projecting 90° from axis of the body (K wing). However, absence of these symptoms does not necessarily indicate freedom of mites.

Infected colonies may not develop normally and may exhibit symptoms of dysentery and an excessive swarming tendency. Often, however, severely infested colonies typically appear normal until their death during the winter. Colonies are most affected during winter confinement and early spring like a stress disease. Mite infestations are at a maximum in the spring when the population is comprised of primarily older bees.

Positive diagnosis can be made only by microscopic examination of honey bee tracheae. In sampling for this mite, one should try to collect either bees that may be crawling near the hive entrance or bees at the entrance as they are leaving or returning to the hive (50 bees per colony sampled). These bees should be placed in 70% ethyl or methyl alcohol as soon as they are collected. Do not collect bees that have been dead for an unknown period because they are less than ideal for diagnosis.

For dissection, each bee should be grasped between your thumb and forefinger, remove front pair of legs and head by pushing them off with a scalpel or razor blade in a downward and forward motion, cut thin transverse section of the prothorax containing the major tracheal trunks with a sharp razor blade, soak disc section overnight with 8% solution of Potassium Hydroxide in water to dissolve muscle tissue, and examine disc sections with a microscope (Minimum 40X. Infested tracheae have various stages of mites and are usually discolored and darkened.

Treatment for Tracheal mites include: 

  • Requeen with Resistant Stock (Buckfast). 
  • Non-Chemical Control Using Grease Patties
  • Chemical Control – Mite-A-Thol™ or Apiguard™

Predators Of Bees

Toads

Toads will often sit by hive entrances to eat bees at night in warm weather. Lizards also sit around hive entrances to eat bees. In the space of a week, a toad can make a significant impact on a strong population of bees.

Dragonflies and Ants

Dragonflies do eat honey bees but they are not voracious eaters and they are generally solitary creatures. Think of them more as population control thats a threat to the hive.

When you discover ants in a beehive, it’s usually a symptom of a bigger problem and could put your hives in serious danger. In fact, when particular species of ants form colonies and happen to cross paths with honey bees, they can fight to the death and significantly harm and even kill a beehive.

Birds

Grey KIngbird or in Creaole Pipirit Bird is a formidable hunter and defender of territory. The bird can be often seen flying through apiaries grabbing bees in flight.

Bees will often gang up on the predator, and attack the bird in its resting spot.

Virgin queens are especially vulnerable to the Kingbird on mating flights.

Emerging Threats - Tropilaelaps Mite

The life cycle of Tropilaelaps mites is very similar to that of Varroa mites in many ways, as both species of mites are external feeders which parasitise the brood stages of the honey bee. 

However, Tropilaelaps mites have a much shorter life cycle, and because of this, have a much greater reproductive rate than Varroa mites. Because of this greater reproductive rate, research has shown that in some hives there can be around 25 Tropilaelaps mites to every one Varroa mite in a honey bee colony. 

However, unlike Varroa mites which can survive on adult bees for quite a few months, Tropilaelaps mites can only live for around 3 days on an adult worker bee as the adult Tropilaelaps mite mouthpiece cannot pierce the adult wall membrane, and therefore, cannot feed on adult worker bees. For this reason, Tropilaelaps mites spend the majority of their life in the brood and will continue to breed and survive in a honey bee colony as long as there is brood present.

A female Tropilaelaps mite will enter worker and drone brood cells that are in the process of being capped and lay 1–4 eggs (though typically 3 or 4). The development from egg to adult takes approximately one week and the adult mites (usually about 2–3) will emerge from the brood cell along with the emerging young adult bee. While in the capped cell the larval/nymph stage of the mite is white in colour and feeds on the developing brood. 

Adult Tropilaelaps mites are active, red-brown mites around 1mm in length and typically 0.5mm wide, about one third the size of a Varroa mite. Considering that Tropilaelaps mites cannot survive for very long on adult bees, the vast majority of adult mites (>95 per cent) will typically mate and re-enter a brood cell to lay more eggs within 2 days of the adult bee emerging from the capped brood cell.

Ready to test your knowledge? Request the final exam for Module 8.