Q Temperatures that kill wax moths and small hive beetles
I am trying to look up the minimum temperatures at which small hive beetles (SHBs) and wax moths can no longer survive so that I can minimize my expenditures on prevention. It is 7:30 a.m. now and it is 50°F (10°C) outside. I understand that it is 95°F (35°C) or so in a hive. However, the temperature in a deadout (a hive in which the colony died) or an extra box on a hive that bees are unable to protect could be much colder, maybe reaching temperatures that would kill SHBs and wax moths. Can they survive overnight temperatures in the 40s (~4.5-10°C) and 50s (~10-15°C) in stored supers without Para-Moth?
New Jersey, September
It appears that temperatures below 13.5°C (~56°F) will kill SHB eggs while no larvae or pupae will develop below 10°C (~50°F). Larvae and pupae can survive for a short period at this temperature, but they will not develop. Unfortunately, there are no complete estimates of how long it would take larvae/pupae to die at these temperatures. I found one manuscript (Noor-ul-Ane and Jung 2021, reference below) that showed the LT50 (lethal time it takes to kill 50% of all individuals) for feeding larvae is 7 hours at 4.9°C (~41°F). For wandering larvae and pupae, the LT50 values are 3.7°C (~39°F) and 5.6°C (~42°F) at 48 hours, meaning those temperatures would have to be consistent for 48 hours to kill half of the wandering larvae or pupae, respectively. The authors also calculated the LT80 values (lethal time it takes to kill 80% of all individuals) for feeding larvae (7 hours at 3.5°C (~38°F)), wandering larvae (48 hours at 2.5°C (~37°F)), and pupae (48 hours at 3.7°C (~39°F)). Finally, the authors also showed that all feeding larvae die at 7 hours of exposure to 0°C (32°F) while all wandering larvae and pupae died after 48 hours of exposure to 0°C. This is helpful information if you plan to freeze/reuse equipment that contains SHB larvae.
Unfortunately, the conditions you specify in your question (nighttime temperatures in the 40s and 50s) have not been tested in research studies, especially when daytime temperatures are warm and food is available. I can only provide a guess concerning what you may see. In the absence of food, “most” SHB larvae will likely die overnight if the temperatures are in the 40s (~4-10°C). You can guess that nearly all would die if these temperatures are sustained for most of the night, on successive nights. You would not get the same level of control if the temperatures were in the 50s (~10-15°C). Oddly enough, I could not find anything about temperatures at which adult SHBs die.
Here are a few manuscripts you can read about SHB thermal tolerance:
- Noor-ul-Ane, M., Jung C. 2021. Characterization of cold tolerance of immature stages of small hive beetle (SHB) Aethina tumida Murray (Coleoptera: Nitidulidae). Insects. 12(5): 459. https://doi.org/10.3390/insects12050459.
- Meikle, W.G., Patt, J.M. 2011. The effects of temperature, diet, and other factors on development, survivorship, and oviposition of Aethina tumida (Coleoptera: Nitidulidae). Journal of Economic Entomology. 104(3): 753–763. https://doi.org/10.1603/EC103643.
- Noor-ul-Ane, M., Jung, C. 2020. Temperature-dependent development and survival of small hive beetle, Aethina tumida (Coleoptera: Nitidulidae). Journal of Apicultural Research. 59(5): 807-816. https://doi.org/10.1080/00218839.2020.1740406.
For wax moths, you can kill all larvae, pupae and adults after freezing 1 hour at -15°C (5°F). It takes 10 hours of exposure to -15°C to kill wax moth eggs, which seem to be the most resilient wax moth stage. This is well within the range of common household freezers. That said, you are more interested in control achieved at environmental temperatures. Apparently, 4°C (~39°F) will cause wax moth activity to cease (no egg hatching, larvae feeding, etc.). Wax moths have been studied a lot longer than have small hive beetles. I expected to find out more about their cold tolerance. However, I really could only find information about freezing wax moths. Thus, it appears the answers to your specific questions are unknown. One can speculate, though, that not many wax moths would die during short-burst exposure to the temperatures and environmental conditions you note in your question. When in doubt, freeze the combs if you are able. I list below a reference for a research project on freezing combs to control wax moths.
- Zhu, X.J., Zhou, S.J., Xu, X.J., Lan, H.H., Zhou, B.F. 2016. Freezing combs as a method for the greater wax moth (Galleria mellonella) control. Journal of Apicultural Research. 55(4): 351-352. https://doi.org/10.1080/00218839.2016.1231457.
Q Drone brood removal
I am exploring the option of using drone brood frames as part of my integrated pest management plan for Varroa. How long should the frames be frozen to kill mites? Other than removing the frames and freezing them before the drones hatch, what else should I be considering? Can drone frames be used in smaller colonies such as 5-frame nucs? Should the frames be removed when the cells are capped?
I am happy to hear that you are attempting to control Varroa using an integrated pest management strategy. As you likely know, drone brood removal cannot serve as an effective Varroa control on its own. Instead, it needs to be paired with other treatment strategies to achieve effective control. The Honey Bee Health Coalition has a wonderful Varroa management guide that includes great information about drone brood removal. You can find the guide, and accompanying website, here: https://honeybeehealthcoalition.org/resources/varroa-management/.
The PDF guide includes information about drone brood removal and other Varroa management techniques, and even a video dedicated to explaining about drone brood removal. The management guide was last updated in August 2022. Information about drone brood removal is summarized in a table on page 28 of the guide. I include that information here as I feel it answers your questions. I wanted to be sure to note that the information below originates with the Honey Bee Health Coalition in their Tools for Varroa Management: A Guide to Effective Varroa Sampling and Control. I add additional explanations, when I feel they are needed, in [brackets].
Technique: Be sure to remove and destroy drone brood [via freezing > 24 hours] once capped. Use drone frames/foundations in brood chamber or comb with elevated drone brood cells.
Route of Exposure: Mites preferentially attracted [to] and reproduce in drone brood; removal of capped drone cell selectively removes mites without harming adult bee population.
Treatment Time/Use Frequency: Treatment at Population Increase [when colony populations are growing] and Peak Population [when colony populations are strongest]. Remove drone brood [from the hive] at 28-day interval (before adult bees emerge).
Time of Year: Only when colonies rear drones (Population Increase and Peak Population)
Registrant-reported Effectiveness: Not as effective as stand-alone treatment; effectiveness compounded by repeating 2 to 3x during Population Increase.
Conditions for Use: Only applicable during Population Increase and Peak Population when colonies actively rearing drones.
Restrictions: Need to remove capped brood in timely manner before adult drones emerge.
Advantages: Inexpensive and effective. Less impactful to the hive than successive comb removal.
Disadvantages: Time consuming management; may be minimally effective. If drone brood is not removed before emergence, it will rapidly increase mite reproduction. Using this method excessively can negatively impact honey production.
Considerations: Use colored drone comb or shallow frame in standard box (stimulating bees to build drone comb from bottom bar) or foundationless frames; cull drone cells built between brood boxes; to improve effectiveness, reduce drone brood on other brood combs to consolidate for easier removal.
You can use this technique for nucs. However, a drone comb ends up using 20% of the comb space (1 in 5 combs) in a 5-frame nuc, opposed to 10% of the comb space (1 in 10 combs) in a full-size hive. Consequently, you can slow the growth of a nuc when dedicating 20% of its comb space to drone rearing/removal.
Q Queen Improvement
My wife has one question. Do bees sleep? I also have one question. When I requeen a colony, how long will it take the new queen to “fix” a poor laying pattern of the previous queen?
Honey bees do not sleep in the same sense that humans do. However, they do have large periods of inactivity that occur throughout the day, and especially at night. In fact, worker honey bees spend the vast majority of their time resting, rather than …
The post The Classroom – May 2023 appeared first on American Bee Journal.