The comb moth is an opportunistic pest that causes serious losses in beekeeping, appearing in both hives and storage. Known as the wax moth, its larvae cause the actual damage. They target unprotected combs when colonies weaken. A strong colony defends itself, but weak colonies or stored combs can be completely destroyed. This pest eats the combs, destroys their structural integrity, and renders bee products unusable.
Species: greater (Galleria mellonella) and lesser (Achroia grisella)
Two primary wax moth species cause economic damage in beekeeping. The most common of these is known as the Greater Wax Moth (Galleria mellonella). It is also the most destructive species. The adult female butterfly’s wingspan can reach around 30 mm. This species’ larvae are very gluttonous. They dig deep tunnels that go down to the comb’s midrib. They especially love brood remnants. They progress rapidly, preferring pollen and beeswax. A dense web layer covers the combs in a short time. The comb structure is completely ruined.
The second species is called the Lesser Wax Moth (Achroia grisella). Its adults are smaller than G. mellonella. The wingspan is generally between 15 mm and 20 mm. The damage from this species remains more superficial compared to the greater moth. It usually feeds on the surface of the combs. It weaves finer and less distinct webs. It mostly prefers the debris (frass) on the hive floor. It also likes pollen-heavy combs. Sometimes it is seen following the destruction started by the greater wax moth. Both species are a serious threat to the beekeeper. Stored combs are especially at high risk.
Biology: Life Cycle and Thresholds
Understanding the biological characteristics of the wax moth is very important. It is necessary to know its life cycle. This information forms the basis of control strategies to be developed against it. This pest’s development depends on environmental factors. Temperature and humidity, in particular, directly affect its development. It is necessary to know the conditions under which the population increases rapidly. This knowledge determines the timing and effectiveness of protective measures. Control must target the most sensitive stages of this cycle.
Life Cycle and Temperature–Humidity Thresholds
The wax moth is an insect that undergoes complete metamorphosis. Its life cycle consists of four distinct stages. These are: egg, larva, pupa, and adult (moth) stages. The stage that causes the main destruction is the larval period. The larvae have an insatiable appetite. Female moths lay hundreds of eggs during their lifetime. It is sometimes observed that they lay 500 to 800 eggs. They lay their eggs in cracks inside the hive. Frame edges or the bottoms of comb cells are also places they prefer.
The development speed is entirely dependent on the ambient temperature. Ideal conditions are high temperatures. Temperatures between 29 °C and 32 °C are ideal. High humidity also accelerates development. A humidity range of 70% to 80% is optimal. Under these conditions, the entire life cycle is completed in a very short time. They become adults in about 6 to 7 weeks. However, as the temperature drops, this duration extends rapidly. Development slows down significantly below 15 °C. When the temperature drops below 10 °C, development almost completely stops. Similarly, high temperatures above 40 °C are also lethal to the larvae. These temperature thresholds are of critical importance. This information is especially used in protecting stored combs.
Signs and Damage
A wax moth infestation is often noticed late. By the time the beekeeper notices it, the damage has already progressed. Early diagnosis is therefore very important. It is necessary to prevent the spread of the damage. Early intervention is vital to save valuable combs. Both the signs inside an active hive and the traces in storage are important. These signs clearly reveal the pest’s presence. The visible traces are a result of the larvae’s feeding habits. They also stem from the waste they leave behind.
Typical Larval Damage Marks on Comb
Wax moth larvae target the most nutritious parts of the comb for feeding. They particularly prefer dark-colored combs. Brood has been previously reared in these combs. There is an important reason for this. These combs do not just contain beeswax. They also contain the shed skins (cocoons) left by bee larvae. There are also pollen residues and small amounts of propolis. These are rich protein sources for the larvae. The larva moves toward the midrib of the comb. It leaves a secretion behind where it feeds. It creates tunnels with this silk-like secretion. These tunnels completely destroy the structural integrity of the comb. It becomes impossible for the bees to repair this comb. The comb becomes unusable for the bees.
Signs: Webbing, Tunnels, Debris, and Odor
The most obvious sign of an infestation is a dense layer of webbing. The comb surface becomes covered with this dirty-white web. The larvae move under this protective webbing. They feed and defecate here. Secondly, distinct tunnel structures are seen. These tunnels extend into the comb. The tunnels are the larvae’s pathways. They quickly turn the comb into a pile of debris. As the infestation progresses, debris accumulates. The larvae’s droppings are seen at the bottom of the hive or under the combs. These droppings are granular, small, and dark-colored. This debris is called ‘frass’. Finally, a heavy odor spreads in a heavy infestation. A smell resembling mold and decay comes from the hive or storage. This odor is a combination of larval secretions and droppings.
Hive-Related and Storage-Related Risk Scenarios
Risks are concentrated in two main scenarios. Hive-related risk usually emerges in weak colonies. Colonies that are diseased or have lost their queen bee are at risk. A colony with a declining population cannot defend itself. For example, colonies covering fewer than 5-6 frames of bees are weak. These colonies cannot protect all combs against moth infestation. The bees cannot clean out the moth larvae. The pest thus multiplies rapidly. A strong colony is different. It notices moth larvae immediately. It throws them out of the hive.
Storage-related risk is the most common scenario. It is also the most destructive. Beekeepers store combs after the harvest. Combs are also stored for spring. If these combs are left unprotected, a great risk arises. Temperatures above 15 °C are especially dangerous. Unprotected combs become an ideal breeding ground for the wax moth. A dark and unventilated warehouse is the riskiest place. A single female moth entering a warm warehouse can lead to disaster. It can cause the total loss of hundreds of combs. This scenario is very serious. The beekeeper’s most valuable asset for the next season is drawn comb. The loss of these combs means major economic damage.
Which Combs Are at Greater Risk?
The wax moth is quite selective. It does not attack all combs equally. The combs at highest risk are specific. These are combs that have seen brood-rearing activity many times. In other words, dark-colored (brown) combs. These combs are very nutritious for larval development. They are rich in protein. They contain abundant pollen residues. They also house the shed skins (cocoons) left by bee larvae. Newly drawn combs are at less risk. White-colored combs used only for honey storage are not preferred. This is because beeswax alone is not a complete food source for the larvae. However, these combs can also be infested. The Lesser Wax Moth (Achroia grisella) in particular may be drawn to these combs. They are also attacked when no other food source remains. Unused, old, blackened combs are at the top of the risk list. Combs that have started to mold are also dangerous. These combs must be regularly destroyed.
Control and Management
Fighting the wax moth cannot be done with a single method. It requires an integrated pest management (IPM) approach. There is no magic solution. The most effective method is to break the pest’s life cycle. It is necessary to create unfavorable conditions for its reproduction. This process begins in the hive. It continues meticulously in the storage area. Preventive measures are always the priority. They are safer and more sustainable than chemical interventions.
Hygiene and Strong Colony Management
The best line of defense against the wax moth is the bees themselves. This is the most natural defense. Strong and healthy colonies are the greatest guarantee. A strong colony covers all the combs inside the hive. The bees patrol regularly. They throw out any moth larvae or eggs they find. They thus naturally prevent an infestation. The beekeeper’s duty is to always keep their colonies strong. This requires using young queen bees regularly. Sufficient food stores must be provided. Effective control against other pests and diseases, like Varroa, must be carried out. Hive hygiene is also critical. Hive bottom boards must be cleaned regularly. Dead bees and comb debris must be removed. These practices reduce the areas where moths can settle.
Freezing (Shocking): Time–Temperature Tables and -12/-15 °C Practices
Freezing is the most effective method for stored combs. It is a method that leaves no residue and is food-safe. This method kills all life stages of the wax moth, including the eggs. The egg, larva, and pupa stages are reliably destroyed. For application, the combs must be placed in a deep freezer. The required time depends on the minimum temperature reached. As the temperature drops, the time shortens. For a safe application, the following practices are recommended:
- -12 °C (minus twelve degrees): Combs should be kept at this temperature for at least 4 to 5 hours.
- -15 °C (minus fifteen degrees): A duration of 3 hours at this temperature is generally sufficient. This time is safe for killing all stages.
- -7 °C (minus seven degrees): If the temperature is higher, the time must be extended. At this temperature, combs must remain in the freezer for at least 24 hours.
During the freezing process, airflow must be provided between the combs. This is important for all combs to reach the target temperature quickly. After shocking, the combs should be allowed to thaw slowly. They need to come to room temperature gradually.
Packaging to Reduce Re-infestation Risk
The freezing process sterilizes the combs. However, this process does not provide permanent protection. The combs are defenseless against future infestations. Combs removed from the freezer must come to room temperature. Afterward, they must be packaged immediately and carefully. This prevents moth butterflies from laying eggs again. Thick, durable trash bags can be used for packaging. Bags that do not tear easily should be chosen. Industrial stretch film is also an option. Large plastic storage containers that can be sealed airtight can also be used. The mouths of the bags must be tightly taped or sealed. Packaged combs should be stored in a cool place. The ideal temperature is below 10 °C. The storage area must be dry, dark, and well-ventilated. Warm attics are the riskiest places for storage.
Biological Agents (Bt, Entomopathogenic Fungi)
Biological control is a safe alternative. It is harmless to bees and humans. It is environmentally friendly and leaves no residue. Today, the most common biological agent is a bacterium. This agent is commercially available. Its name is Bacillus thuringiensis (Bt). The aizawai serotype (Serotype 7) is particularly effective. This bacterium produces a protein that is toxic only to wax moth larvae. Bt is mixed with water. It is sprayed onto the combs to be stored using a sprayer. The larvae eat the comb containing the Bt spores. Their digestive systems become paralyzed. They die within 2-3 days. This bacterium is completely harmless to bees. It is also harmless to humans and other mammals. This is because the toxin only becomes active in the alkaline gut environment of the moth larvae. Research also exists on entomopathogenic fungi. For example, Beauveria bassiana is being studied. However, Bt is currently the most widely used biological solution.
Limits and Safety of Chemical Fumigation
Chemical fumigants (gassing agents) are risky. They can leave residues in honey and beeswax. For this reason, they are banned in many countries. Or their use is severely restricted. For example, Paradichlorobenzene (PDB) crystals were widely used in the past. However, this substance accumulates highly in beeswax. It carries a carcinogenic risk. Sulfur dioxide (burning sulfur strips) is another fumigant. It kills larvae and adult moths. However, it is ineffective against wax moth eggs. This is a serious problem. Therefore, the application must be repeated approximately 2-3 weeks later. This is not a practical solution. Furthermore, sulfur vapor is highly corrosive to metal equipment. It also carries a serious fire risk. Acetic acid vapor (at 80% concentration) is effective against the moth. It also controls some disease agents like Nosema. However, its use is dangerous. It is a very strong corrosive agent for comb frames and metal equipment.
Evaluation and Application
It is necessary to measure the effectiveness of the methods used in wax moth control. This measurement is important for both scientific research and practical beekeeping. There are ideal results obtained in the laboratory. They are obtained under controlled conditions. However, real-world applications in the field can be different. The conditions in the apiary, warehouse, or hive are variable. The criteria that define success must be clarified. This helps beekeepers choose the most accurate method.
Differences Between Laboratory and Field Methods
In a laboratory setting, control methods are tested under standard conditions. These conditions are controlled. For example, a specific number of wax moth larvae are taken. Usually, 2nd or 3rd instar larvae are used. These larvae are placed on a small piece of treated comb. The comb may have been treated with Bt or frozen. Temperature (e.g., 30 °C) and humidity (e.g., 75%) are kept constant. These tests clearly show the mortality rate of an agent. It is seen whether high rates like 99% or 100% are achieved.
Field methods (or field trials) are different. They reflect real warehouse conditions. Here, temperature and humidity fluctuate during the day. They also change seasonally. Control success is not measured only by the number of dead larvae. The level of damage to the combs is also important. For example, the goal is for less than 5% of the combs to be damaged at the end of a 6-month storage period. It is checked whether re-infestation has occurred. Field conditions test the practical validity of laboratory data. They show the method’s durability.
Evaluation Criteria
Multiple criteria are used when evaluating the success of a control method. The first and most basic criterion is the mortality rate (%). That is, how many of the target pests died after the application. The egg, larva, or pupa stages are examined. The second important criterion is the comb protection level. It is assessed how many (as a percentage) of the combs remain undamaged. How little damage they sustained is also a measure. The third criterion is the method’s duration of protection. That is, how long the application prevents re-infestation. For example, a Bt application is expected to provide protection until the next season. The most meaningful criterion for the beekeeper is different. It is whether the combs are in a condition to be given to a bee colony the following spring.
Conclusion and Practical Takeaways
The wax moth is a secondary pest for the beekeeping industry. However, it can be potentially devastating. It poses a major threat, especially during the storage phase. It threatens the beekeeper’s labor and capital. Its management requires proactive prevention. It is necessary to focus on hygiene and hive health. Direct chemical intervention should be the last resort. Strong colonies can provide their own defense. The beekeeper’s real responsibility, however, begins with the combs that the bees are not tending to.
Summary of Key Findings
The key findings in wax moth control are based on the pest’s biology. The pest’s dependence on temperature is critical. The biggest threat comes from the Galleria mellonella species. This species highly prefers old combs. Combs containing brood remnants are at risk. Moth development stops below 10 °C. The most effective control methods are clear. Freezing (shocking) is residue-free and safe. Biological agents like Bacillus thuringiensis (Bt) are also effective. Strong colony management is the primary and most natural line of defense.
Actionable Takeaways for the Beekeeper
The practical steps for beekeepers are clear. These steps should form a routine.
- Colony Strength: Colonies must always be kept strong. Weak colonies should be combined or supported. Excess combs that the bees are not covering must be removed from the hive.
- Comb Renewal: Old combs must be regularly renewed every year. Blackened and damaged combs must be replaced. At least 20% of the combs (e.g., 2-3 frames in a 10-frame hive) should be removed from the hive.
- Storage Preparation (Freezing): Combs should not be moved to storage right after harvest. Combs taken from the hive should also not be left waiting. They must first be frozen (e.g., at -15 °C for at least 3 hours).
- Storage (Packaging): Combs coming out of the freezer must be packaged in an airtight manner. Thick bags or containers must be used.
- Storage Conditions: Combs should be stored in the coolest place possible. Below 10 °C is ideal. The storage area must be dry and well-ventilated.
These steps minimize the risk of the wax moth. They ensure the beekeeper’s comb capital is protected.
