Researching Hive Colony Collapse

Unexplained bee deaths last spring all but wiped out thousands of hives in the Coromandel, Raglan and Wairarapa areas. Dr Mark Goodwin of Plant & Food Research is heading a group looking at determining the role of three bee gut parasites in the deaths. There are many unknowns including whether this was a one-off event or whether it will be ongoing, the effect of high concentrations of hives in these areas, seasonal effects, or whether all or none of these possibilities is the cause.

If this situation does recur, the result could be a major problem for the honey industry and the country’s pollination services.

Spring in beehives is typically the time when bee numbers start to build from winter lows. By September a hive may have around 10,000 inhabitants and by November, when nectar availability and honey flow are at the maximum, there might be 15,000 workers beevering away.

However, in spring 2014 there were reports of unexplained losses of bees. Many hives in the Coromandel area were reduced to a queen and around 200 workers. They were surviving, but only just. Dr Mark Goodwin, head of Plant & Food Research’s bee unit, talked with beekeepers in the area and found that the problem was widespread.

“Initially we thought it was just one beekeeper but then we had a meeting and others reported the same thing,” says Mark.

“Then we heard similar stories from the Wairarapa, Raglan throughout the spring. It involved thousands of hives. Some beekeepers lost 20 to 30% of their hives and 60% of their honey crop.”

Bees die for all sorts of reasons and Mark says that you can often tell by looking at colonies what they had died of, perhaps a disease or maybe because the beekeeper had done something wrong, but in this case the symptoms had not been seen before.

“When we tested the bees we found they had very high levels of Nosema apis, a gut parasite, but that is not unusual because it has been in New Zealand for as long as bees have been here,” he says. “However, they also had Nosema ceranae, another species of gut parasite that was first found in the country about six or seven years ago in the Coromandel. It has a worldwide distribution and at some stage jumped species from Apis cerana, the Asian honey bee, which is significant because that is where Varroa came from. Because Nosema ceranae hasn’t been around for very long, everybody around the world is still trying to work out what this means for our bees.”

As if the Nosema microsporidian parasites weren’t enough, testing identified a third parasite, Lotmaria passim. Mark says that very recent studies in Belgium have linked Lotmaria passim and Nosema ceranae to colony collapse disorder (CCD). “It’s very complex. We have these very high levels of three parasites but whether they are the cause or whether they are an effect of something else we don’t know. The symptoms fit the definition of CCD but we can’t be sure if it is CCD because nobody around the world can agree on what is the cause,” says Mark.

“These parasites attack the gut lining of the bees, which starve to death because they can’t absorb nutrients and the colony collapses quickly. You don’t see dead bees anywhere, and that’s typical for bees – when they are sick they leave the hive and that’s a behaviour that attempts to get rid of the infection.”

“We know they don’t leave together but we don’t know how far they go. They just disperse and we have found it is actually quite an effective control strategy that for these parasites and the colony usually survives that initial collapse. The queen and a few hundred bees will keep going and by the autumn they will be a reasonable population again, but it is way too late to get any honey.”

The Plant & Food Research Bee Unit also heard reports of more colonies than usual dying over late autumn and winter 2014, so it was a complex event and it is difficult to predict what might happen in the future. It might never happen again or perhaps it might skip a few years or it may happen every year from now on.

“It won’t be until well into spring that we will get a really good idea whether this is an ongoing problem or a one-off, but my guess is that it is not a one-off. Whether it needs a particular set of conditions to make it occur again we don’t know. It might not be the parasites at all but something else that we haven’t identified yet,” says Mark.

“For example, it might be the result of something that happened in the autumn. In the affected areas there are vastly more hives than there used to be because of the demand for manuka honey. Could it be that there was a pollen shortage in the autumn, that bee nutrition was poor over winter and coming into spring, or was it something completely different?”

“All we know is that the bees disappear and that there are high levels of these pathogens. What happens before that we just don’t know. And the tricky thing with this sort of research is that we could set up an extensive trial this season and the problem may not recur.”

Mark’s group is in the process of looking to see if there is a correlation between the levels of Nosema in hives and what happens afterwards, and in particular they want to sample Nosema levels in bees of different ages to see if and how the concentration of the organism in their gut changes over the season. Normally it is impossible to tell how old a bee is but Mark has developed a method of age marking.

“We take a frame that is about to hatch and put it in an incubator. When bees first hatch out they don’t sting and you can handle them quite easily. We have a team of people to mark 5000 of them with a dob of paint on the thorax,” he says.

“Every two weeks we put a batch into the hives that we are studying so that we have known age groups. Then we can sample some of each age group and work out concentrations of the pathogens and also see what they do to the lifespan.”

“We also have a group of colonies where we have eliminated Nosema with chemicals so that we can compare their lifespan with that of infected bees to see if there is a difference.”

Time will tell how significant these bee deaths are in terms of both honey and pollination services. Mark says it is getting harder and harder to keep up with the demands for pollination. Around 180,000 bee colonies are needed each year for paid pollination services.

“These colonies are prepared to a certain standard before being moved into a crop, and we have noticed more recently there have been difficulties getting colonies to the standard required for pollination,” says Mark.

“When people audit the colonies they find that they are all a bit weaker than they should be, and that means it will be harder and harder to provide enough bees – the number of colonies might be the same but the numbers of bees inside each one might be lower. We are already seeing that sort of pressure, and problems like bee diseases, deaths and CCD just make it more difficult. That’s why we need to identify the cause or causes.”

“The interesting thing is that in Australia they have Nosema ceranae and Lotmaria passim but there are no reports of the same thing happening there, which suggests that it is a little more complicated than just the presence of two organisms. And not every colony that has these organisms has fallen over.”

“Another factor could be environmental conditions. In New Zealand and elsewhere we are seeing these massive stocking rates to get manuka honey. It’s a bit like putting thousands of cattle together in huge feedlots and having to feed them antibiotics to keep them from dying of diseases, and there have been big concentrations of hives in Coromandel, Raglan and the Wairarapa and we keep hearing reports from other places in the North Island.”

“So in summary we don’t know that it is true CCD but it is very serious and we need to find some solution to it because if it continues at the same level it is a big problem, and if it increases it will be a major problem.”