The Great Wax Moth Invasion!
By: Dodie Stillman,
Wolf Moon, Snow Moon; did you know that the full moon in March is referred to as the Worm Moon? I love the full moon, but during my first year of beekeeping a love/hate relationship developed!
In the August TBS Monthly issue, Mary Reed – Chief Apiary Inspector of Texas, shared information with us on Chalkbrood, a viral infection that is often considered a “secondary” disease. A secondary disease is one where it’s not likely the reason a colony dies, but it does have the potential to significantly weaken it.
I’m going to cover one of the secondary pests beekeepers must face. This brings us back to the March Worm Moon, and the secondary pest Galleria mellonella, commonly called the Greater Wax Moth (GWM). They are also known as the web (or wax) worm, the bee moth, and the wax (or bee) miller. There are a few other species - the Indian Meal Moth, the Bumble Bee Wax Moth, and the Achroia grisella, or Lesser Wax Moth, that can also cause problems.
This moth is found almost world-wide, and definitely in our honey bee colonies in Canada, the United States and Mexico.
In the late evenings and on full moon nights, you can see the female moths flying near and trying to enter honey bee colonies.
March is the perfect time to start thinking about this moth, as they are most active in the summer months, and like many pests maintaining a large healthy colony can effectively control wax moth infestations, so build your colonies up during the month of the worm moon!
The GWM is only between ½” to ¾” long, with the female being slightly larger; they are gray in color and their folded wings are triangle shaped. Females enter the colonies at night (again the full moon!) and lay eggs in old comb and hive crevices. She can lay several hundred eggs, and prefers to lay them in dark brood comb or comb that has debris and honey bee casting due the additional nutrients found there, as opposed to lighter brood or honey comb.
The larvae that hatch in between 3-30 days and are the real enemy. They feed on wax, cast skins, and pollen, and will continue to do this as they mature and grow.
Greater Wax Moth larvae start out a pinkish-white color and become a darker gray as they age, they have a brown head and are about 3/4” long.
As the GWM larvae tunnel through the comb, they leave a silken trail that is so dense the honey bee workers find it difficult to remove the larvae especially if the infestation is high. Larvae take between 28 days and 6 months before pupation. As the GWM reaches the end of its larval stage, it will spin a tough white silk cocoon. You can find these between frames, in the crevices of the frames and all over the inside of the woodenware. A sure sign of a previous infestation in your hive bodies are the oval pill-shaped gouges in the wood that were chewed away while in the pre-pupal stage
Photograph - Ashley Mortensen, Univ. of Florida
Because the Greater Wax Moth Larvae can overwinter in these cocoons, the duration taken by the moth to complete its life cycle varies from weeks to months. The length of time is affected by amount of food, diet composition, as well as temperature and humidity.
The pupa can develop and hatch within 3-8 days in warm conditions. The female Wax Moth can live about 12 days, while the males can live up to 21 days. The GWM can undergo between 4–6 generations annually.
It’s important to note that the Greater Wax Moth larvae have feet all along their bodies. This differs from the Small Hive Beetle that only has 3 sets of legs near its head.Both of these pests are common in honey bee colonies so being able to tell them apart is essential. Another difference is the Small Hive Beetle larvae feasts on honey, pollen, and brood, where the GWM larvae consumes and destroys our honey bees' other precious commodity, honeycomb.
Larvae photo from the University of Georgia College of Agricultural and Environmental Sciences webpage
Video courtesy: NSW Tocal College Doug Somerville
Integrated Pest Management The potential of transmitting honeybee viruses has raised real concerns to find sustainable integrated pest management strategies. For example, fecal pellets of the larvae were found to contain spores of Paenibacillus larvae, the bacteria that causes American Foul Brood. Additionally, Israeli acute paralysis virus and black queen cell virus have been detected in larvae. Large scale infestation of colonies by larvae often lead to colony loss and absconding.
The most effective management of the GWM is by keeping your colonies strong with adequate food stores, as well as sealing cracks and crevices. You should also adjust your hive size based on population and strength.
Cultural practices include starting with resistant strains of honey bees, like bees selected for hygienic behaviors. In addition, beekeepers should replace frames/combs regularly, and destroy heavily infested frames.
You can interrupt the development cycle of the GWM by either super heating or freezing your equipment. Because heating will sag and distort wax, it’s best to freeze frames and beekeeping equipment.
There is also a need for beekeepers to provide proper storage for hive frames and equipment that could be susceptible to attack by the GWM. The first method of storage is to place frames in such a way that they receive plenty of sun and air flow. The second option is to store frames using paradichlorobenzene crystals, ParaMoth, or Moth Crystal (not mothballs!).
It’s always a good idea to freeze any frames you suspect might have GWM eggs or larvae. Let them return to room temperature before you store them.
Photos by: Dodie Stillman
As beekeepers, it is our responsibility to take care of our honey bees. Helping them stay strong and healthy will allow them to fight off the secondary diseases and pests.
By - Dodie Stillman
The Biology and Control of the Greater Wax Moth, Galleria mellonellahttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC5492075/ Honey Bee Diseases & Pests 3rd Edition Canadian Association of Professional Apiculturists Texas Apiary Inspection Service https://txbeeinspection.tamu.edu/wax-moths/ Bee Aware https://beeaware.org.au/archive-pest/wax-moth-18/