State of the nation: bees
How are bees doing in New Zealand?
There’s a lot of buzz about bees all over the world right now, not just because of the vital role they play as pollinators but due to the increasingly complex range of threats they face from diseases and parasites, climate change, nutritional stress, pesticides and modern agriculture.
In other parts of the world, honey bee populations have markedly declined – scientists in Europe and America have cited losses in some colonies of more than 50 per cent. But the situation in New Zealand is different: over the last few years the population of bees – that is bees in managed colonies where they receive regular treatment to help manage the threat of varroa – has been steadily increasing here.
On the back of “manuka madness”, New Zealand now has more beehives than Australia or Canada. Not per head of population – more in total. From just 250,000 managed hives here in 2005 – five years after varroa mite first appeared – we now have approaching 750,000 managed colonies. If the price of maukau honey stays high and the number of beehives continues to increase at the same rate, we could see more than a million hives here within the next few years. In comparison Australia has lost more than 30 per cent of its commercial operations since 2008, dropping from 2000 beekeepers running more than 50 hives to around 1400 beekeepers running more than 50 hives.
Could we reach “peak bee”? It’s hard to say, according to Barry Foster, board member at industry body Apiculture NZ. “Bee numbers vary from season to season, but now that we are heading towards 700,000 hives the question that needs asking is: can our ecosystem take a million hives or even more?”
We’ve heard of black gold (oil) and white gold (milk) – now yellow gold (manuka honey) is all the rage. The annual value of New Zealand’s honey exports for the 12 months ending November 2015 – 80 per cent of which was manuka honey – increased by 45 per cent to $281 million. New Zealand really is the land of milk and honey – but we don’t yet know the possible consequences of having so many managed hives will be.
Especially since one threat to bees rarely mentioned is poor beekeeping. Failure to feed, inadequate varroa management, failure to report and destroy colonies affected by American foulbrood all create weaker hives, which makes them more susceptible to robbing out.
Last year, the Ministry of Primary Industries (MPI) and the beekeeping industry commissioned the country’s first bee health and colony loss survey. Almost 40 per cent of beekeepers responded to the call to provide baseline data for future surveys and research. The results, reported in March this year, found beekeepers reported bee colony losses of 11 per cent. Compare this with the 17 per cent loss reported in a similar Northern Hemisphere survey (where varroa has a problem for much longer). Landcare Research has been commissioned to repeat the survey, which launches this month.
Among the many threats that bees face, the best known is varroa mite, which arrived here in 2000 and quickly spread. This parasite feeds on a bee’s blood, shortening its lifespan and weakening the colony. It’s now so widespread that it is assumed that bee colonies here can survive only with human intervention and treatment.
But resistance of varroa to control products is a problem all over the world. There can be up to 20 generations of the mite each year and because they reproduce sexually, they quickly build up resistance to chemical controls.
“We have resistance to some synthetic chemicals here now,” says Professor Peter Dearden of Otago University, who is working with various groups to breed varroaresistant bees.
“So beekeepers have to change up or combine treatments, but research is needed into better techniques in varroa control and the associated pathogens they inject into bees.”
And of course varroa is just one of the challenges bees face today. Last year, Gisborne-based diagnostic laboratory dnature identified a new parasite ( Lotmaria passim) found in a Coromandel beehive, which attacks the intestine of bees, making them susceptible to other diseases such as nosema. Ongoing testing suggests that it is now widespread in New Zealand and has been present for at least the past five years.
European foulbrood and the Israeli acute paralysis virus are established in Australia and many scientists
From just 250,000 managed hives in 2005 we are now approaching 750,000 – and 1 million hives is not beyond the realms of possibility
Varroa reproduce rapidly and soon build up resistance to chemical treatments. There can be up to 20 generations of the mite a year
believe only it’s a matter of time before they make inroads here too.
American foulbrood is already widespread in New Zealand and the giant willow aphid was first spotted here in 2013. These aphids tap into the tree’s phloem and when they pull away, the phloem keeps coming. Wasps feed on this sticky substance and if they enter beehives, the bees fill up frames with honey they can’t metabolise, and then expend even more energy cleaning out the hive.
Sprays containing neonecintinoids are still for sale in New Zealand (banned now in several places overseas), and exposure to these has also been linked to colony decline.
Bee breeding is under scrutiny too. Some suggest breeding bees to be more passive – so beekeepers can extract honey without being attacked – has made them more susceptible to disease as they don’t fight back when disease-bearing wasps and feral bees invade their hive and steal the honey. However there is overseas research that gives some cause for hope. Researchers at Washington State university have discovered that the feral bee population was increasing there which suggested that those bees – that is, bees not living in a managed beehive – had developed some natural resistance to varroa. It’s not possible to do similar research in New Zealand however, as Kiwi scientists have no idea just how many feral bees were here before varroa arrived, says Dr Mark Goodwin, who leads the apiculture and pollination research team at Plant & Food Research. One study in Hamilton, which looked at whether feral bees were more or less likely than managed colonies to be affected by American foulbrood, revealed 106 feral colonies in and around the city. “But we never knew if 106 was all there was or whether we were only finding one in 10 or one in 100.
We’ve never had a survey of feral bees before varroa, and we have no idea how many there are now.”
Before varroa arrived, Mark says, sightings of feral bees – descendants of the more aggressive Northern European black strain which were the first honey bees brought here – were common. Now, you only see the docile yellow Italian strain, which is used by beekeepers. “Possibly that is because there are so many managed hives around now. If a queen bee from a feral colony went out looking for a mate, it’s likely the first she would come across would be an Italian drone.”
It has been assumed that the feral bee colonies that do exist in New Zealand post-varroa come about when a swarm leaves a managed colony and sets up a new home in a suitable site, taking varroa with them. “And because there is nobody to treat them,” Mark says, “in a year or two varroa will have wiped that hive out.”
There is anecdotal evidence, however, of feral bee colonies surviving for years – Mark says he has heard of some that appear to have survived for 10 or even 20 years.
And that is something this scientist is keen to investigate further. “Our hypothesis, and it is a hypothesis, is that if these feral colonies are surviving over several years then either the bees are setting up home in a tree and there is something about that tree which the varroa mites don’t like, or something about the genetics of the bee has changed so it now has a natural resistance to the mite.”
Mark says that the scientists now need to know the location of these feral bee colonies. With this in mind, NZ Gardener is calling on its readers to be part of a citizen science project. Let us know the location of any feral bee colonies you are aware of. Feral colonies live in cavities, so make their homes in wall and roof cavities, in structures like bridges, occasionally caves, and in hollowed out trees. As well as the location, Mark would like to know what the bees are nesting in (if it’s a tree, let us know what kind of tree) and how long the hive has been there, if you know. Email the details to mailbox@nzgardener.co.nz.
The most obvious sign of a feral bee hive is bees flying in and out of a hole, plus you’ll often see beeswax at the entrance, Mark says. “Remember there are wasps nests, as wasps are cavity dwellers too. So you have to be able to tell the difference between a yellow jacket and a bee. But wasps don’t carry pollen. So if you see the brightly coloured balls of pollen on the legs, you’ll know it’s a bee.” ✤