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  • Writer's pictureJohn Mackay

Are You Seeing Signs of Nosema in Your Hives?

ADVERTORIAL: dnature Diagnostics and Research

As beekeepers we know how to pick the signs of American foulbrood (AFB) and deal with it, but are you as clued up on the traits of the two nosemas? Spring Dwindling Disease can be devastating, so it pays to know what you’re looking for and how to go about confirming and remedying their presence. Molecular biologist John Mackay of dnature lab in Gisborne brings you up to speed.

As strips start to go into boxes (our own included), our thoughts also turn at this time of year to an issue that first arose back in the spring of 2014. Coromandel beekeepers Oksana Borowik and John Bassett had noticed that hives were suddenly losing bees. Fast!

John Bassett had communicated these losses to Gisborne beekeeper Barry Foster and before long, we had samples of the remaining bees from these hives. At the same time, we had samples coming in from Wairarapa beekeepers who were trying to understand why their hives – strong at the first spring inspection – were suddenly collapsing.

COROmandel and WairaRAPA generated a name for the syndrome we were seeing: Cororapa. You can see what we did there. These hives had similar clinical pictures:

  • Formerly strong hives suddenly losing bees over 2-3 weeks

  • Plenty of honey and pollen stores

  • Typically still queen-right, with a small cluster of bees

  • Despite low numbers of bees, these hives didn’t suffer robbing

  • No dead bees outside the hive or on the baseboard

So … What Was It?

In our lab, we take a 10-bee sample and extract the DNA and RNA from these bees. This material can then be tested for nosemas and American foulbrood (DNA) and bee viruses such as Deformed Wing Virus (RNA). Using quantitative DNA testing methods allows us to see the pathogen levels present in the sample – the same technology that we would all come to learn about six years later when COVID hit.

Technical director John Mackay at work in the dnature Diagnostics and Research’s lab which offers beekeepers a range of diagnostics tests for pathogens of honey bees, including AFB, nosema ceranae and nosema apis.

We tested the samples for all the pathogens we could at the time. Most showed low or no levels – but two stood out: Nosema ceranae (only discovered in New Zealand four years earlier) and Nosema apis (the “invisible honey tax” as Mark Goodwin calls it). The samples from these hives in Coromandel and Wairarapa were showing much higher levels of both these nosema species – with Nosema ceranae showing levels approximately 10 to 100 times higher than Nosema apis.

Nosemas are fungal-like organisms – microsporidians to be exact. There are two main nosema species in honeybees and while it has seemed in many countries that Nosema ceranae was ‘replacing’ Nosema apis, both are commonly found.

What Will Nosema do to Your Hives?

Nosema ceranae has been associated with major colony losses in the USA and Europe and, for a time, was considered a major cause of the Colony Collapse Disorder in the USA. Nosema ceranae has a number of effects on honeybees – encouraging foraging behaviour through altering hormone levels while disrupting the homing ability of those same foragers. Bees are recruited at an earlier age to replace the lost foragers and the colony enters a downward spiral.

The combination of both nosema species is a double hit – a report in 2014 involving David Tarpy (who will be speaking at next year’s Apiculture New Zealand conference) showed that bees without a nosema infection lived an average of 27 days in the lab; infection with one or other strain was a decrease to 20-21 days, while an infection with both species led to a further 25% drop in lifespan to 15 days (Milbrath et al., 2014). This decrease in the longevity of the bees, combined with the other effects of nosemas, helps explain the observed signs in New Zealand colonies.

While colonies collapsed and died, Plant and Food Research scientists – together with Oksana –showed that using the same hiveware the following season led to a similar result. A heat treatment process was tested and showed that the bees readily took to the treated combs with increased brood and fewer spores in the bees.

At the same time, and with the encouragement of Oksana, we developed a new test for the detection of a very new pathogen: Lotmaria passim. Well actually the name was new – the pathogen had been around for some time, but believed to be something else! The discovery of L. passim in New Zealand caused some concern, but has been shown to be widespread and not necessarily associated with the rapid colony dwindling. This was backed by Masters research from Tammy Waters in our lab, under the supervision of Prof Phil Lester at Victoria University of Wellington.

Beekeepers should look out for the signs of nosema in their hives and, if in doubt, take a sample of 10 to 20 bees and freeze them for potential lab analysis at dnature,

How do you know if Nosema is Present?

To confirm the Cororapa picture a DNA test is required. It is the only way to confirm the presence of both nosema species and the levels of both will also be indicated. This is important, as bees will often have low levels of different pathogens that cause little issue. A test – which includes both species plus L. passim – is $80 for the 10 bee sample. Should the presence of Cororapa be confirmed, then the infected gear can be marked for treatment (or comb replacement), while some companies have tested their products as treatments against nosemas, in the form of additives to sugar syrup and patties.

If you’re not sure about getting a test, take the 10-20 bee sample into a small container and euthanise by freezing the bees overnight. With bees in the freezer you have testing options . . .with empty boxes and frames, you have only uncertainty. The issue has been widespread in the North Island – including my own hives back in 2016. There’s a story there about prying the racks off the home oven in order to heat frames to the 50 degrees, but don’t tell my wife!

Talk about it

The way in which the affected beekeepers dealt with the discovery of this syndrome demonstrated lessons that should serve us well. The beekeepers in Coromandel talked about it with their colleagues and discovered that 14 of them were affected by the same issue. More conversations got ourselves and Plant and Food scientists involved as well as the Ministry for Primary Industries.

Getting a fatal disease in your hives does not make you a poor beekeeper – it’s what you do and who you tell after the fact, that determines that.



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