Biosecurity – What Does the Colony Loss Survey Teach Us?

With a recent hornet incursion in Auckland, biosecurity is the topic-du-jour within apiculture and so Colony Loss Survey author Pike Stahlmann-Brown explains what last year’s survey results indicated about beekeepers’ preparedness.

By Pike Stahlmann-Brown

Beekeepers have until 28 November to complete the Colony Loss Survey.

A queen Vespa velutina (Asian hornet or yellow-legged hornet) building a nest was discovered in Glenfield on Auckland’s North Shore in mid-October, then two more later in the month. This species of hornet – whose native range stretches from Afghanistan to Malaysia – preys on insects including honey bees returning to their hives from foraging. Yellow-legged hornets hunt for protein (honey bees, other insects etc.) to feed their larvae. Predatory pressure outside the beehive reduces honey bee foraging activity, increasing stress in the colony and leading to depletion of stored honey, making colonies susceptible to starvation. The effects can be significant: yellow-legged hornets invaded France in 2004 and were estimated to have weakened between 30% and 80% of beehives following the initial detection.

Biosecurity New Zealand responded quickly and destroyed the Glenfield nest, but the emergence of a new threat to honey bees is understandably concerning for beekeepers. As Radio New Zealand reported, Comvita’s chief executive Karl Gradon said “This could not have come at a worse time”.

The 2024 NZ Colony Loss Survey included questions about new pests and diseases establishing in New Zealand. Specifically, the survey asked, ‘If an exotic bee pest or disease did arrive in New Zealand, how confident are you that the biosecurity system could detect it before it has a chance to spread widely?’. Among commercial beekeepers, 8% reported being “Very confident” that a new pest or disease could be detected, 55% were “Somewhat confident”, and 37% were “Not at all confident”.

The survey also asked beekeepers to evaluate their own ability to identify signs of four pests and diseases that are not present in New Zealand, namely small hive beetle (Aethina tumida), European foulbrood (Melissococcus plutonius, EFB), Tropilaelaps mites (Tropilaelaps sp.), and tracheal mites (Acarapis woodi).

Small hive beetles are black beetles around 5–7mm long. They scatter quickly when hives are opened, with their 10mm larvae burrowing through comb transmitting a yeast which causes the honey to ferment or “slime out”. EFB produces spotty brood patterns as well as dead, discoloured (often yellow), and sometimes twisted larvae in uncapped cells. A hive infected by EFB can smell like ammonia. It can often be difficult to distinguish from American foulbrood (Paenibacillus larvae) in the field. Tropilaelaps mites are reddish brown and one-third the width of varroa; they are very active and can be spotted mostly in the brood. Tracheal mites produce K-deformed wings and darkened trachea on adult bees; however, positive identification requires laboratory diagnosis.

If you suspect any of these exotic pests or diseases in your hives, call the MPI Exotic Pest & Disease Hotline on 0800 80 99 66.

Among commercial beekeepers, 51% were either “Somewhat confident” or “Very confident” that they could detect signs of small hive beetle in their apiaries. 46% were at least somewhat confident that they could detect signs of European Foulbrood, and 32% were at least somewhat confident that they could detect signs of Tropilaelaps mites. In addition, 29% were somewhat or very confident that they could identify signs of tracheal mites.

Pike Stahlmann-Brown.

While confidence in identifying new honey bee threats is encouraging, several beekeepers who attended the New Zealand Honey Bee Research Symposium in August noted that overconfidence in one’s own ability can have serious implications for the wider industry. With some pests and pathogens being fast-spreading, even small delays in detection can have serious consequences for the wider industry.

The 2024 survey also asked, “How confident are you that the biosecurity system could eradicate exotic bee pests and diseases from New Zealand?”. Among commercial beekeepers, 2.5% were “Very confident”, 22.5% were “Somewhat confident”, and 74% were “Not at all confident”. While the responses suggest a cautious outlook, they reflect the complexity of the challenges involved in eradication.

These biosecurity questions were a special topic in the 2024 NZ Colony Loss Survey. In addition to its usual focus on varroa management and over-winter losses, the 2025 survey includes special topics on wasp management and sources of advice about beekeeping (as well as trust in those sources). The 2025 survey also paints a fuller picture of pollination.

The 2025 survey will be open until 28 November. If you haven’t completed it yet, a reminder with your unique survey link will be sent on 3 November. If you don’t receive the email, send your Apiary Registration Number to surveys@landcareresearch.co.nz and I’ll send you a new link.