Shocking Surge in New Zealand Bee Colony Losses Signals Urgent Varroa Threat

New Zealand's honey bee populations have taken a significant hit, with the latest data revealing that nearly 13 percent of the country's bee colonies perished over the winter of 2025. This alarming figure, drawn from the comprehensive New Zealand Colony Loss Survey 2025, underscores the growing dominance of the varroa mite as the primary culprit behind these devastating losses. Managed by researchers at the Bioeconomy Science Institute, the survey gathered responses from almost 2,000 beekeepers overseeing more than 148,000 colonies, extrapolating to an estimated total of 495,587 colonies nationwide. The loss of 63,435 colonies not only strains beekeepers but also poses risks to the nation's agriculture, given honey bees' critical role in pollination.

Decoding the Varroa Destructor Mite: Nature's Tiny Destroyer

The varroa destructor mite, often simply called varroa, is an external parasite that latches onto honey bees and their larvae, feeding on their hemolymph—the insect equivalent of blood. This feeding weakens bees, stunts development, and transmits deadly viruses like deformed wing virus. First detected in New Zealand in 2000, varroa has evolved into a persistent challenge despite decades of management efforts. Adult female mites reproduce within capped brood cells, multiplying rapidly if unchecked, turning strong hives into 'varroa bombs' that reinfest neighboring colonies. In the 2025 survey, varroa was blamed for 7.0 percent of all healthy colonies entering winter—more than double the 2024 figure of 4.6 percent and the highest on record—surpassing all other causes combined.

Historical Trends: A Steady Climb in Losses Since 2017

Since monitoring began in 2017, overall winter loss rates have fluctuated but trended upward, peaking in 2021 before a brief respite in 2024. The 2025 rate of 12.8 percent mirrors 2023's 12.7 percent but marks a sharp reversal from 2024's 10.8 percent. Varroa-attributed losses have risen consistently until last year's dip, now rebounding alarmingly. Other factors like queen problems (around 2.8 percent), suspected starvation (0.5 percent), and wasps (0.4 percent) have remained stable, highlighting varroa as the variable driver of escalating mortality.

This table illustrates the concerning trajectory, with varroa emerging as the dominant threat.

Regional Hotspots: Lower South Island Bears the Brunt

Loss rates varied significantly by region, with the Lower South Island recording the highest at around 19.2 percent—far above the national average. Factors like cooler winters exacerbating mite stress and apiary crowding contribute here. Commercial operations dominate nationwide (95 percent of colonies managed by 10 percent of beekeepers), yet hobbyists (77 percent of beekeepers managing 5 percent of colonies) suffered 26 percent higher varroa losses due to less rigorous treatment regimens.

Photo by Yulin Wang on Unsplash

Beekeeper Practices Under the Microscope: Treatments and Gaps

All commercial beekeepers treated for varroa in 2025, employing record levels of formic acid, tau-fluvalinate, oxalic acid strips, and vaporization. However, perceived treatment success declined, possibly due to mite resistance development. Hobbyists lagged: 0.6 percent untreated, 22 percent treated once (vs. 6 percent commercial), and 31 percent used a single method (vs. 13 percent). Pike Stahlmann-Brown, principal researcher at the Bioeconomy Science Institute, notes, "Hives not treated at the right time become varroa bombs." Synchronized area-wide treatments could mitigate re-invasion.

• Formic acid: Broad-spectrum, temperature-sensitive.
• Tau-fluvalinate: Synthetic pyrethroid, resistance risks.
• Oxalic acid: Effective on phoretic mites, multiple applications needed.

Beekeepers also destroyed over 12,200 wasp nests, aiding biodiversity.

Economic Ripples: Billions at Stake in Pollination and Honey

Honey bees underpin New Zealand's $5 billion annual pollination services, vital for kiwifruit (55 percent of services), avocados (44 percent), apples/pears (25 percent), and berries (22 percent). The 2025 losses equate to millions in replacement costs—past estimates peg 2021 winter losses at $24 million for commercials alone ($38 per colony). Honey production, especially high-value mānuka, faces pressure, while horticulture risks yield drops without sufficient pollinators. Globally, New Zealand's 12.8 percent loss is low compared to 30-40 percent elsewhere, but sustained rises threaten food security and exports. For deeper insights, see the full 2025 Colony Loss Survey.

University-Led Innovations: Breeding Varroa-Resistant Bees

New Zealand universities are at the forefront of sustainable solutions. A 2025 thesis from Victoria University of Wellington by T. Pilkington examined the Proposed Resistant Strain (PRS) honey bees, bred over years for innate mite resistance traits like grooming and hygiene behaviors. This work aims to reduce chemical reliance. Plant & Food Research, collaborating with the University of Auckland's Photon Factory, explores laser technology to zap mites precisely. A 2022 study by J. Sainsbury et al. identified SNP markers for Varroa Sensitive Hygiene (VSH), enabling marker-assisted selection to breed resilient stocks. These academic efforts promise long-term hive health. Explore the VUW research here.

Collaborative Strategies and Wasp Warriors

Beekeepers eradicated 12,200 wasp nests—49 percent controlled pests via traps (half), direct killing (41 percent), or baits (33 percent). Barry Foster, a Gisborne commercial beekeeper, stresses collaboration: "Beekeepers not treating simultaneously allow reinfestation." Trusted advice sources include peers, clubs, and scientists, with calls for better science dissemination. The survey, modeled on international COLOSS standards, positions NZ favorably globally.

Photo by Matthew Stephenson on Unsplash

Future Outlook: Hope Through Research and Unity

While 2025 losses alarm, NZ's rate remains enviable. Synchronized treatments, resistant breeding, and tech like lasers offer paths forward. Universities and CRIs like Manaaki Whenua drive innovation, while policy supports biosecurity. Beekeepers seeking advice value scientific input highly. For the infographic summary, visit MPI's resource. Proactive management can safeguard pollination-dependent crops and honey exports.

Actionable Insights for Beekeepers and Stakeholders

To combat varroa:

• Monitor mite levels monthly via alcohol wash or sugar roll.
• Treat in autumn pre-winter, using integrated methods.
• Collaborate regionally for area-wide management.
• Source VSH-tested queens for resistance breeding.
• Support university trials for emerging tech.