Helping honeybees

Honeybees are critical to US agriculture, which relies on pollinators for crop production. Varroa destructor (Varroa mite) is a pest that threatens the safety and survival of honeybee colonies. Infestation is one of multiple causes of colony collapse for honeybees.^1,2

This ectoparasite reproduces in capped worker and drone brood cells in the hive while feeding on the brood or adult honeybees.³ Feeding on adults and larvae can cause weakened immune systems, decreased body weight, and shortened lifespans for the honeybees, according to the US Department of Agriculture (USDA) Agricultural Research Service (ARS).¹

There are other honeybee stressors that lead to colony collapse, such as weather, nutrition, hive management, and queen-related issues,² as well as pesticides. However, in dvm360 interviews, the Varroa mite was labeled the “No. 1” enemy of honeybees by apiculture experts Jörg Mayer, DVM, MS, DABVP, DECZM, DACZM; Kaitlyn Krebs, DVM, MBA; and entomologist Erin Jones, PhD.

They also mentioned that Varroa mite feeding isn’t the only way these parasites can damage a colony. “The Varroa mites can vector several viruses to honeybees, which makes them more of a problem than if they didn’t vector the diseases, so they are No. 1 on our list for things that we need to look out for and treat for,” Jones said.

Among the vector viruses introduced into a hive by Varroa mites are acute bee paralysis virus, Kashmir bee virus, Israeli acute paralysis virus, and parasitic mite syndrome (PMS). Some signs of PMS, which can kill a colony, are a spotty brood pattern, a sick brood that appears sunken into the cell, a lack of eggs or developing larvae, bees with deformed wings, and a decreasing adult population.¹

Another virus introduced by Varroa mites is deformed wing virus (DWV).¹ Mayer, a professor of zoological medicine at the University of Georgia College of Veterinary Medicine in Athens, said DWV prevents a honeybee from flying. “Therefore, it can’t provide any pollination services,” he added.⁴

In early 2025, the USDA determined that approximately 1.7 million commercial beekeeping colonies had been lost since the previous summer. Upon investigating these collapsed colonies, agency investigators found high levels of DWV and acute bee paralysis in all bees sampled by the USDA.⁵

“There are a lot of different drugs and regimens out there to try to control [the Varroa mite]. We can’t really eradicate the Varroa mite anymore. It’s established well everywhere,” Mayer said.⁴

Advancing honeybee medicine

Combating drug resistance

Amitraz, a pesticide that is toxic to Varroa mites, has a favorable safety margin for honeybees when it is used appropriately. However, the mites are becoming increasingly resistant to amitraz due to genetic mutations. A study conducted by investigators with ARS and the University of California, Davis combined amitraz with a compound used in pesticide research.⁶

“This compound inhibits a naturally occurring process that prevents certain chemicals, like pesticides, from accumulating inside cells,” Julia Fine, PhD, a research entomologist at the Pollinator Health Research Laboratory in Davis, California, said in a news release.⁶ “If a chemical toxicant can’t reach a high enough concentration in a cell, it won’t have a toxic effect in the organism. Previously, we didn’t know if this process was part of how Varroa tolerate amitraz exposure.”

The investigators found that the toxicity of amitraz increased and was effective against amitraz-resistant mites when the inhibiting compound was used in combination with the pesticide. The findings may lead to the development of novel synergists to control Varroa mites, according to the investigators.⁶

Exploring new technology

RNA interference (RNAi) is a promising adjunctive novel technology that may help control Varroa mites by targeting the root cause of colony collapse.⁶ The RNAi treatment with the active ingredient vadescana (Norroa; GreenLight Biosciences) showed promise in some studies published in 2026.^7,8

One 13-week study of mite control treatments found that vadescana was effective in controlling mite levels for approximately 10 weeks while improving the lifespan and health of bees.⁶ Another study found that the vadescana RNAi treatment was effective for managing Varroa mites, especially in colonies that began the investigation with low levels of these parasites. At the conclusion of this 44-week study, investigators found that a higher dose was needed at the field site with larger colonies and mite loads, and that the treatment’s duration did not last as long at that location. However, 45% of colonies receiving high-dose vadescana survived the winter, whereas only 7.5% of colonies receiving no treatment of Varroa mites survived.⁸

In a continuing education lecture at the 2026 Veterinary Meeting & Expo in Orlando, Florida, Jones discussed RNAi as a promising treatment for controlling Varroa mites as an emerging technology for honeybee veterinary care.⁹ “The RNAi [is a] biopesticide. It prevents Varroa mites from breeding or reproducing…. [We] can be very hard pressed to find chemicals that are going to kill our pests, that are not going to kill our bees. The advantage [of RNAi] is that it is only going to affect the target pest,” Jones said.

“We have a lot of [drug] resistance that has developed with Varroa mites. [RNAi] is a new technology for us that they’re not going to have resistance to yet. It is going to be safe for the environment, more sustainable control. It has been approved by the [Environmental Protection Agency] and is available on the market for beekeepers,” Jones added during the lecture.⁹

Caring for honeybees in general practice

“General practitioners can absolutely care for bees, and they have to be the ones who are caring for them. People think of bees as production animals, but in my experience, most veterinarians caring for bees are actually small-animal practitioners…. As veterinarians, we have a responsibility to the bees, and I think that encompasses both large- and small-animal veterinarians,” Krebs, an associate clinical professor at Rowan University Shreiber School of Veterinary Medicine in Harrison Township, New Jersey, as well as a beekeeper, said in an earlier interview.¹⁰

Veterinary professionals who are not yet well versed in caring for honeybees should seek out additional training and education on how to properly care for them. Krebs, Jones, and Allie Donaldson, DVM, a past president of the Honey Bee Veterinary Consortium (HBVC), cited the HBVC as a valuable resource for veterinary practitioners seeking knowledge about honeybees. The HBVC provides annual conferences, certification programming, networking opportunities, and more.^10-12

“We formed this consortium to help support veterinarians in learning about bees, learning about honeybee medicine, and [learning about] how we as veterinarians can support beekeepers, support the beekeeping community, and…bring our expertise with science, medicine, and herd medicine…into beekeeping,” Donaldson said in a dvm360 interview.¹¹

Jones also noted 3 pathways for veterinarians to get involved with bees: contacting a local extension agent with connections to apiculture, joining a bee club, and getting 2 to 3 beehives for the experience.¹²

Takeaway

An Integrated Pest Management (IPM) protocol is widely recommended for the health of a honeybee colony. This is a multipronged, ecologically based approach that relies on a variety of methods and resources. An IPM plan should include prevention strategies, such as managing the space around the hives (eg, with pest-resistant plants) and setting a threshold for when to take action, then monitoring and continuing to identify pests, such as Varroa mites.^13,14

Pest control methods are also part of the IPM, followed by evaluation. “Effective, less risky pest controls are chosen first, including highly targeted chemicals, such as pheromones to disrupt pest mating, or mechanical control, such as trapping or weeding. If further monitoring, identifications, and action thresholds indicate that less risky controls are not working, then additional pest control methods would be employed, such as targeted spraying of pesticides,” the Texas Apiary Inspection Service said.¹³

References

1. What is a Varroa mite? USDA ARS. April 5, 2023. Accessed April 20, 2026. https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/research/varroa/varroa-overview/
2. Ellis JD. Other stressors of the hive. Presented at: Veterinary Meeting & Expo; January 16-20, 2026; Orlando, FL.
3. Varroa mite life cycle and reproduction. USDA ARS. Updated January 27, 2021. Accessed April 20, 2026. https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/research/varroa/varroa-mite-life-cycle-and-reproduction/
4. Mayer J, Crossley KC. Varroa mites and their effect on honeybees. dvm360. January 28, 2025. Accessed April 20, 2026. https://www.dvm360.com/view/varroa-mites-and-their-effect-on-honey-bees
5. Canaday A. USDA researchers find viruses from miticide resistant parasitic mites are cause of recent honey bee colony collapses. News release. USDA ARS. June 2, 2025. Accessed April 20, 2026. https://www.ars.usda.gov/news-events/news/research-news/2025/usda-researchers-find-viruses-from-miticide-resistant-parasitic-mites-are-cause-of-recent-honey-bee-colony-collapses
6. Ryan J. Finding more effective treatments in the fight against Varroa mites. USDA ARS. News release. February 19, 2026. Accessed April 20, 2026. https://www.ars.usda.gov/news-events/news/research-news/2026/finding-more-effective-treatments-in-the-fight-against-varroa-mites
7. Merk J, Anastasi M, McGruddy R, Manley B, Felden A, Lester PJ. Longevity and foraging performance of honey bees treated with an RNAi-based Varroa destructor biopesticide. Sci Rep. 2026;16(1):8208. doi:10.1038/s41598-38557-w
8. McGruddy RA, Felden A, Baty JW, et al. RNAi can be effective for the control of Varroa destructor in honey bee colonies. J Apic Res. Published online March 27, 2026. Accessed April 20, 2026. doi:10.1080/00218839.2026.2622814
9. Jones E. Future directions in honey bee veterinary medicine. Presented at: Veterinary Meeting & Expo; January 16-20, 2026; Orlando, FL.
10. Krebs K, Crossley KC. Caring for honey bees in general practice. dvm360. June 21, 2024. Accessed April 20, 2026. https://www.dvm360.com/view/caring-for-honey-bees-in-general-practice
11. Donaldson A, Crossley KC. Networking with honey bee veterinarians. dvm360. January 26, 2026. Accessed April 20, 2026. https://www.dvm360.com/view/networking-with-honey-bee-veterinarians
12. Jones E, Crossley KC. Gaining more experience with honeybees. dvm360. January 19, 2026. Accessed April 20, 2026. https://www.dvm360.com/view/gaining-more-experience-with-honey-bees
13. Texas Apiary Inspection Service. Integrated pest management. Texas A&M University. Accessed April 29, 2026. https://txbeeinspection.tamu.edu/beekeepers/integrated-pest-management/
14. Jack CJ, Ellis JD. Integrated pest management control of Varroa destructor (Acari: Varroidae), the most damaging pest of (Apis mellifera L. (Hymenoptera: Apidae)) colonies. J Insect Sci. 2021;21(5):6. doi:10.1093/jisesa/ieab058
15. North American bee strategy unveiled to protect pollinators and strengthen honey market. Honey Bee Health Coalition. December 1, 2025. Accessed April 20, 2026. https://honeybeehealthcoalition.org/north-american-bee-strategy-unveiled-to-protect-pollinators-and-strengthen-honey-market/
16. Ellis JD. Common pests of honeybees and their control. Presented at: Veterinary Meeting & Expo; January 16-20, 2026; Orlando, FL.