Honey Bee Pests, Predators and Diseases

Honey bee pests, predators, and diseases are a constant threat to the survival of different types of bees. Bees are important pollinators and a vital part of the ecosystem. European honeybees like the A. Mellifera and other different types of bees play a crucial role in agriculture. Without bees, human beings would not be able to sustain sufficient food resources to survive within a few years. It is therefore essential to implement control measures to protect the different types of bees from pests and diseases and to provide excellent care.

Honey Bee Predators: Mammals in the Bee Yard

Depending on the geographical location, different types of bees have different natural enemies. In the United States, bears, honey badgers and skunks are some of the most common predators of bees. Although, opossums and raccoons are also known to attack bee hives occasionally. To get to the sweet delicacy, the predators have developed different strategies. 

Skunks for example scratch at the hive entrance. The guard bees become alerted and investigate. When a sufficient number of adult honey bees appear at the hive entrance, the skunk uses the opportunity to devour the tasty snack, spitting out the remnants of bees. 

Bears are not as subtle as skunks. They use brute force and are known to cause substantial damage to hives. After discovering a hive for the first time, they often return repeatedly to go after the sweet honey. Such attacks can cause substantial damage, often destroying entire honey bee colonies. Effective control measures against these attacks are electric fences. 

Monkeys and other primates also prey on honey bees, particularly in various tropical parts of Asia. Monkeys were observed opening hives, consuming honey and the brood. The destroyed frames often made the colonies abscond. As a preventative measure beekeepers wire the lids to the boxes, and the boxes to each other. This makes it more difficult for the monkeys to get to the sweet treat.

It is important to mention that among the primate pests of honeybees, humans are most likely also the most destructive. Human misuse of pesticides in modern-day farming accounts for a greater loss of bees than the loss from all other causes combined.

Avian Predators

In Africa, Asia and parts of Australia and Europe, adult bees face another predator, the bee-eater bird. These birds live in colonies and have a long down-turned bill (beak). They predominantly feed on flying insects, in particular bees and wasps, which they catch in flight. To remove the stinger and discharge most of the venom, the bee-eater bird developed a unique strategy. It repeatedly hits and rubs the insect on a hard surface.  Although a single bird or even a few birds seldom cause a serious problem, large flocks can cause significant losses of adult bees. 

A pest for beekeepers, the farming industry considers these birds as beneficial because they help control insect pests on farmland. Control measures are therefore limited and bee keepers can only solve the problem by carefully selecting the sites for their apiaries and temporary relocate the hives until the migration period is over.

Honey Bee Predators: Amphibians and Reptiles

In tropical climates, honey bees face another type of enemy that is not easily detected by beekeepers. Amphibians, such as the Asian common toad (Bufo melanostictus), the banded bullfrog (Kaloula pulchra), the Rana limnocharis, also known as rice field or Asian grass frog, and the Asian Bullfrog (Rana tigrina) usually attack the hives at night. Both, toads and frogs have a similar method of attack; They wait close to the hive entrance and prey on passing bees.

The only visible trace of these attacks are the dark brown droppings with remnants of bees inside that are often found in front of the hive entrance.  Healthy honey bee populations of moderate to large size generally withstand the reptile attacks and fully recover, however, smaller colonies cannot. Beekeepers often fail to notice the problem unless the size of the colony shrinks significantly. To protect the hives raising them to a height of 40 to 60 cm is often sufficient unless there is a large population of amphibians. In this case the hives can be protected by fine-mesh chicken wire.

Reptiles

In Asia, reptiles like the tokay gecko, forest lizards like the Calotes sp, Acanthosaura sp (commonly known as mountain horned dragons), Sphenomorphus skinks and other lizards are commonly known to also attack bees near the hive entrance or on flowering trees visited by worker bees. Also in on the takings is the nocturnal Hemidactylus frenatus gecko, a small lizard known as common house gecko. It often hides in the empty space between the covers of the hive. In a weak colony, it can cause a sudden loss of the queen in tropical areas.

Unfortunately beekeepers have little control to combat these predators. However, raising the hives and coating the legs with grease can help to prevent the reptiles from climbing up to the hive entrance. Another measure of prevention is  frequently cutting shrubs, tall grass and dense bushes that are known hiding places of these reptiles.

Honey Bee Predators – Insects

Small Hive Beetle

Another natural enemy of the bee is the small hive beetle (Athina tumida). Originally endemic to sub-Saharan Africa, it has spread to other continents like North America, including Mexico, Australia, and the Philippines. The small hive beetle is a destructive pest that consumes the eggs laid by honey bees and lays its eggs on the honey bee comb. At the larval stage, small hive beetle larvae feed on the honeycomb, honey, and pollen. While tunneling their way through the combs, the larvae defecate, causing the honey to discolor, ferment and froth, making it unusable for consumption. Depending on the severity of the infestation, the bees often abandon their hive. 

Preventative Measures to Control the Small Hive Beetle

The most effective tactic to prevent infestation of the small hive beetle is good beekeeping management. This includes keeping the hive clean, keeping hives and frames in good condition, reduce stress from disease, and strengthen weak colonies among other tactics. Rotten, cracked or warped hive bodies are perfect hiding places for the small hive beetle. Debris left to accumulate on a bottom board is the perfect place for beetle larvae to complete pupation inside the hive. This can be prevented by regular cleaning or using screen bottom boards that prevent a build-up of debris.

Beekeepers can usually prevent a major infestation by maintaining a manageable adult hive beetle population as it is the beetle larvae that causes the biggest destruction. There are also various mechanical trap designs on the market to control the adult small hive beetle in the hive.  Combining cultural and mechanical controls generally helps to control beetle infestations within a manageable range.

Asian Giant Hornets

As the name suggests, the Asian giant hornet is the largest hornet species worldwide. Workers grow to 1 ½ to 2 inches (3.8 to 5.1 cm), with a wingspan of 3 inches (7.6 cm) and a stinger measuring ca. ¼ inch (0.6 cm), whereas queens can grow even larger. Originally from Asia, the insect has also spread to the western coast of the United States. First sightings were recorded in December 2019. The Asian giant hornet prefers to live in low forests and mountains, typically nesting underground in nests they either dig into the ground, or, in existing tunnels dug by rodents. They primarily feed on other insects and attack bee nests, destroying entire colonies. Due to its large mandibles that can decapitate prey, a single giant hornet can kill as many as 40 bees per minute!

Asian giant honey bees have developed their own ingenious way to defend their nests against predators like the giant hornet. Each individual bee flips its abdomen after the bee to one side of them in a sequenced, coordinated manner across the entire nest, creating a continuous wave-like motion through the colony.

Since the 1970´s, humans used different methods to exterminate the Asian giant hornet, including beating, nest removal, bait traps, mass poisoning, protective screens and trapping at the hive entrance.

Wax Moth

There are two species of wax moth that can cause substantial damage to a honey bee colony. They are the Greater wax moth (Galleria mellonella, and the Lesser wax moth (Achroia grisella). The most significant difference between both is that the greater wax moth is the more destructive and common pest, whereas the lesser wax moth is both less destructive and less prevalent. Both species are distributed almost worldwide wherever there are honey bees, however, they seem to prefer warmer rather than colder climates.

In the hive, wax moths are usually found in warm, dark places with poor ventilation. This is usually in top bars and inner covers, where they lay their eggs. Once hatched, the larvae immediately start tunnelling through the comb, defecating as they burrow their way through brood cells and honey in the process. Removed or damaged cell caps in the brood comb sometimes leads to bald brood. Worker bees chew the rest of the capping, exposing their pupaes´heads, which can lead to deformed legs or wings in newly formed adult bees.

To prevent wax moth infestation it should be said that this pest can never be completely eliminated. It is therefore important for beekeepers to keep their hives meticulously clean and practice good colony management. Treating wax moth with chemical treatments bears a high risk of contaminating the honey and the honey bee colonies, and is therefore not recommended. A better strategy to control wax moth infestation is to use temperature control, better ventilation and more light.

Wasps

The western yellowjacket (Vespula pensylvanica) is another predator of honey bees. These wasps prey and scavenge on insects, caterpillars and spiders for food. Honey bees are one of their favorite insects. Killing and devouring individual bees, they also raid hives for larvae, pollen, and honey to feed. Yellowjackets are common in temperate climates from Mexico to North America, including the Hawaiian islands.

Yellowjackets are aggressive honey bee predators, and are often found near the entrance of a hive, ready to ambush and kill individual bees. The honey bees are dismembered after the kill and some parts are eaten with the remainders brought back to their nests to feed their own larvae. The honeybee´s primary defense mechanism against these predators is to fight the intruders with stings, and around a dozen of honey bees cluster around single yellowjackets, ¨cooking¨ them to death with body heat. These clusters can generate around 120 degrees Fahrenheit (49 degrees C). Even strong hives often cannot withstand the attacks of the yellowjackets and collapse. Yellowjackets can smell chemicals that reveal weakness in a hive. This triggers an all-out assault by chemically signaling for reinforcements. Subsequently the yellowjackets loot the honey cells, killing the bees and often the queen.

The pest can be controlled with chemical sprays, hanging traps, and electric zappers. Natural alternatives are peppermint oil, hanging up an imitation nest, or using a protein bait like fish, liver, or chicken.

Natural Enemies of Bees: Mites, Parasites, Spiders

Flower crab spiders (Misumena vatia) are carnivorous. Endemic to Europe and North America, they are commonly found on goldenrod sprays and milkweed plants. These honey bee predators feed on invertebrate insects, and often kill prey with their paralyzing venom much larger than themselves. Flower crab spiders can change color depending on what prey they feed on. Their name stems from their unique ability of moving sideways like crabs in addition to moving backwards and forward. 

Flower crab spiders usually hunt during the day. These sneaky spiders wait hiding on a flower or on the ground for prey  to pass. When a victim is close, it grabs the prey with its forelegs and quickly injects its paralyzing venom. The subdued prey is injected with digestive enzymes from the fangs of the spider, before sucking out the rendered bodily liquids. When prey is scarce, they also feed on nectar and pollen. 

Tracheal and Nosema Ceranae Mites

The Tracheal mite (Acarapis woodi) is a microscopic, white colored mite that lives in the respiratory system of the honey common in Europe, North America and parts of Asia. Invisible to the naked eye, it infects and reproduces inside the honey bee’s breathing tubes (tracheae). Tracheal mites feed on hemolymph (blood) and spread from bee to bee or through swarming and absconding. Infected bees suffers from respiratory problems and become sick and weakened with a significantly reduced lifespan. Until now, the only reliable method to diagnose a tracheal mite infestation is by laboratory examination.

Having said this, there are tell tale signs of a serious tracheal mite infestation. For example, large numbers of crawling honey bees at the hive entrance that lost the ability to fly and go out to forage. Also, honey bees holding their wings at strange angles (‘K wing’), and bees appearing disorientated.

Nosema Ceranae Mite

This serious disease of adult European honey bees is caused by spore-forming unicellular parasites called Nosema apis. Bees become infected when they ingest Nosema spores. The spores germinate in the bee´s midgut, entering the cells and absorbing nutrients. In the midgut, the spores either infect new cells or, they are expelled in the bee´s feces. Infection can be spread by other bees ingesting the spores from contaminated food and water sources. Alternatively, the spores can be spread when cleaning contaminated combs, or by robbing contaminated hives.

A single worker bee can produce several million spores. The disease can cause serious losses of adult bees and colonies in autumn and spring. Infected bees display symptoms like trembling, swollen, greasy-looking abdomens, or holding their wings at odd angles. Other tell-tale signs are yellow or golden drop marks.

Unfortunately, there is no reliable diagnosis for Nosemosis. Some of the general symptoms are easily confused with other factors that affect honey bee colonies. Given that Nosema cannot be seen by the naked eye and causes very general symptoms, it is often called as ‘silent killer’.

Varroa Mite Infection

 

Varroa mites are the biggest honey bee predators. The mites (Varroa destructor and V. jacobsoni) are tiny red-brown external parasites that can only reproduce in a honey bee colony of the species Apis cerana and Apis mellifera. They feed and live on adult honey bees but their main diet is the larvae and pupae of the developing brood. Varroa mites attach to the bee´s body and weaken it by sucking its fat body. The fat body is a section of tissue that holds fat cells,  glycogen, protein, and high concentrations of mitochondria and enzymes and can be compared to a human liver and fat storage.

Infested honey bees are weak and suffer from malformation. The varroa mite also transmit numerous viruses. These include the RNA virus Deformed Wing Virus, Acute Bee Paralysis (ABPV), Kashmir Bee Virus (KBV), and Israeli Acute Paralysis Virus (IAPV). Parasitic Mite Syndrome (PMS) occurs in colonies with high varroa infestation and has a range of symptoms. These include sick brood that appear melted into the cell, which is often mistaken for European Fouldbrood or American Foulbrood. In addition, it causes a spotty brood pattern, capped brood cells that are damaged or torn open, a lack of eggs or larvae, and bees with deformed wings. Other visible signs are a fast dwindling adult population and visible mites attached to bees or walking on the comb. Varroa mites are the biggest reason of colony collapse.

Controlling Varroa Mites

There are various cultural, mechanical and chemical methods to control varroa mites, each has its advantages and disadvantages. It is crucial to understand the implications of each method. Soft or hard chemicals should only be used as a last resort as mites can build up resistance. Several studies are examining the impact of chemicals on honey bees. Rotating treatments and monitoring the mite infestation is crucial in order to effectively manage this pest.