Jumping to the conclusion of “mite resistance” can be a big mistake, when varroa damaged hives are discovered. That’s the warning from proponents of mite monitoring, who say regularly testing hives for varroa mite loadings is the easiest way to gain an understanding of what might be going wrong.
The need for a better understanding of varroa mite loads in New Zealand has been highlighted by the loss of hives to the parasite and the viruses it carries this autumn, say those behind the Mite Monitor project.
Concern of mite resistance to some synthetic treatments is nothing new, with varroa having been confirmed in New Zealand since 2000 and therefore subjected to repeated use of some miticides. This autumn the issue has been raised again.
Beekeepers around the Te Puke, Bay of Plenty, area say they are seeing higher than usual losses due to varroa damage, despite having previously effective treatment regimes in place.
In spring, Te Puke sees thousands of hives moved in, many from outside the province, to help pollinate the many kiwifruit orchards in the area. Congestion of hives aids mite drift between hives and this not only impacts hive health through higher mite loadings, but some beekeepers say it is getting harder to kill those mites.
However, jumping to the conclusion of “mite resistance” runs the risk of inaccurately diagnosing the problem and therefore potentially missing better solutions, South Island beekeepers Martin Laas and Rae Butler say.
Laas and Butler are the driving force behind the Mite Monitor programme, which brought together Canterbury beekeepers to regularly monitor their hives for varroa mite over the past beekeeping season. Only by gaining an understanding of the infestation level of, first, individual hives, then the collective hives of a region and ultimately New Zealand, will we be able to best understand and solve some of the key concerns with varroa, such as reinfestation and resistance, the team at Mite Monitor say.
“If you are not monitoring as you take your autumn treatment out, to see what your mite levels are, then it is very easy to say ‘my treatment has failed’,” Laas warns.
“That is because you assume there were high mite levels when you took the strips out. As we have found though, it can go from zero to very high quite quickly, depending on what is happening around you.”
Butler recently witnessed an example of this, in a friend’s hives. Mite loadings were tested when varroa treatments went into two hives in early March, with a mite count of two in 300 bees in both hives. That count had lowered to 1/300 on removal of the treatment on April 30. However, the hives were showing signs of viruses by mid-May and so another count was taken in both hives, resulting in 63/300 and 16/300.
“It is impossible for the mites to replicate that much in that period, so horizontal reinvasion is presumed,” Butler says.
“If we hadn’t carried out our alcohol-wash tests, or alternatively sugar-shakes, then we would have been in the dark and could have, wrongly, assumed the treatments had not worked.”
To help beekeepers better understand the range of factors which can lead to high mite loadings following treatments, Laas has created a flowchart (see next page) to work through. Before exploring the possibility of resistant mites, the flowchart sees a beekeeper determine if the product was used correctly, if there has been reinvasion, or if they have received a faulty product.
“Before you blame your neighbour, or the manufacturer, you should ask and answer the questions at each step,” Laas says,
“I am finding people jumping to the resistance step, and I am not saying there isn’t some resistance, but it is hard to take people seriously when they haven’t considered the other options.”
Mite monitoring in autumn is particularly important, as that is when varroa problems often manifest. Those beekeepers in the Mite Monitor program were encouraged to test a representative sample of their hives with alcohol washes four or five times in the season, firstly in late winter/early spring, then as spring treatments came out, followed by a mid-honey flow test. Further testing was sought before autumn treatments went in and upon their removal.
That sort of testing regime will help any beekeeper better understand what factors are influencing varroa populations within their operation. Ideally, a programme such as Mite Monitor would be replicated nationwide though, to assist a range of research – including the always topical issues of “mite resistance”, Laas says.
“If we could get it rolled out across the country it could be a very useful dataset for research organisations to use, for things such as determining what treatments are working best.”