Since the introduction of varroa as a new parasite in Western beekeeping, various methods have emerged to manage this parasitic disease. However, improper use of these methods can lead to frustration among beekeepers and even an unhealthy obsession with eradicating the mites entirely. It’s crucial to understand that continuous treatment isn’t viable as it only eliminates a portion of the varroa, particularly when brood is present. Therefore, there’s a growing emphasis on understanding the population dynamics of varroa and its relationship with honey bee colonies to identify more efficient treatment and management approaches tailored to different stages of development. This understanding underscores the importance of monitoring the parasite’s evolution alongside the bee population to design integrated pest management (IPM) strategies1,2 that minimize parasitic impact without disrupting colony development or reducing productivity.
Long-term strategies aim to foster a state of coexistence between bees and varroa, like in Apis cerana, such as selecting bees with specific hygienic behaviors (VSH)3, 4 to detect and remove mites from cells. However, despite these efforts, commercial options for successful varroa management remain limited, and achieving significant progress may take several years. Therefore, in the daily reality of beekeeping, maintaining healthy hives relies on three pillars: monitoring, management, and acaricidal treatments. Varroa monitoring provides essential data on parasite status, enabling beekeepers to make informed decisions and intervene before infestations reach critical levels.
Is monitoring crucial?
Absolutely! Evaluating the parasite load and comparing it with the capped brood quantity and overall vigor of the colony is vital to avoid delaying therapeutic decisions.
How to monitor and how to interpretate the results
Commercial devices or methods involving powdered sugar, alcohol-water mixtures or CO2 facilitate monitoring by assessing varroa levels in nurse bees. Interpreting monitoring results is crucial, with acceptable threshold values continually evolving and being reduced.
See summary of methods4
| Method | Sensitivity | Accuracy | Ease of use | Time required | Recommended use |
| Visual inspection | Low | Low | High | Moderate | Not recommended |
| Brood dissection | Moderate | Low | High | Moderate | Supplemental to other methods |
| Sugar shake | Moderate | High | Moderate | Moderate | Perform repeatedly throughout season |
| Alcohol wash | Moderate | High | High | Low | Perform repeatedly throughout season |
| Sticky board mite drop | High | Low | Moderate | High | Supplemental to other methods, sensitive for low populations. |
Modern standards consider 2-3 varroa per 100 bees as a moderate rate5, while higher levels can significantly impact colony health and honey production.
Resources like the “honey bee health coalition” website and smartphone applications such as “MiteCheck” aid in monitoring and data sharing for statistical analysis. To know more you can download Varroa guide here.
When to start monitoring
Monitoring should start in spring6 and continue throughout the productive season, including during acaricidal treatments, to ensure effectiveness and anticipate re-infestations. Spring marks the initiation of varroa mite management, providing crucial insights into post-winter conditions and predicting future trends. Given the exponential mite population growth rate7, initial assessments are pivotal. Monitoring mites remains essential throughout the productive season, extending into autumn and winter. Vital to monitor during acaricidal treatments for efficacy; hives with mesh bottom boards facilitate mite fall observation on Vaseline-coated plates. Lack of mite drop signifies treatment inefficacy, rectifiable promptly. Continuous monitoring instils confidence in hive health, forewarns parasitization risks, and aids in interpreting re-infestations. Biomechanical control methods like drone breeding, health swarms, or queen caging offer effective means to curb mite proliferation.
Monitoring Considerations
Maintaining vigilance without delay is crucial; delays in addressing varroa mite growth can prove costly. Unexpected population surges may occur even in seemingly healthy or recently treated hives, emphasizing the need for proactive monitoring. Assuming uniform parasitic conditions across all hives is a fallacy; variability exists despite identical management. Sample representativeness is critical, including hives of varying strengths and locations within the apiary. A representative sample, comprising at least 10 hives8, should include both weaker and stronger colonies, with attention to hive ends where bee drift is higher. Drones play a pivotal role; colonies with substantial drone brood may initially show moderate or low infestation rates, but subsequent drone emergence can exacerbate mite migration to worker cells, escalating parasitic symptoms rapidly. Continuous presence of the parasite must be acknowledged; absence during routine checks doesn’t negate its presence. Numbering hives facilitates tracking parasitic trends within individual hives. Treating the entire apiary as a unified therapeutic unit is essential; even slight variations in colony vigor necessitate uniform management, ensuring simultaneous application of measures across all colonies.
Neglecting certain hives may lead to reinfestations. The concept of establishing a lazaret apiary becomes intriguing when considering a secluded location to isolate heavily infested hives that serve as mite reservoirs for nearby ones.
Ultimately, shifting from reactive treatment to proactive prevention entails a mindset change, recognizing the need for continuous monitoring to uphold hive health and effectively control varroa infestations in a sustainable manner.
References and links of interest:
- Keith S Delaplane, Jennifer A Berry, John A Skinner, James P Parkman & W Michael Hood (2005). Integrated pest management against Varroa destructor reduces colony mite levels and delays treatment threshold. Journal of Apicultural Research, 44:4, 157-162, DOI: 10.1080/00218839.2005.11101171
- RUFFINENGO, Sergio R et al. Integrated Pest Management to control Varroa destructor and its implications to Apis mellifera colonies. Zootecnia Trop. [online]. 2014, vol.32, n.2, pp.149-168. Available in: http://ve.scielo.org/scielo.php?script=sci_arttext&pid=S0798-72692014000200006&lng=es&nrm=iso. ISSN 0798-7269.
- O’Shea-Wheller, T.A., Rinkevich, F.D., Danka, R.G. et al. A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission. Sci Rep 12, 4852 (2022). https://doi.org/10.1038/s41598-022-08643-w
- Honey bee medicine for the veterinary practitioner, Terry Ryan Kane and Cynthia M. Faux, 2021 Wiley Blacwell. ISBN 978-1-119-58337-0.
- https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/research/varroa/how-to-monitor-sample-and-treat-for-varroa/ https://www.mpi.govt.nz/dmsdocument/59209-Re-imagining-varroa-monitoring-A-practical-approach
- WOAH, Manual terrestre de la OIE 2021, cap 3.2.7 Varroosis de las abejas melíferas (infestación de las abejas melíferas por Varroa spp.). https://www.woah.org/fileadmin/Home/esp/Health_standards/tahm/3.02.07_Varroosis.pdf
