Marco Moretti made a valid comment to the sugar shaker post. It doesn’t surprise me that Antonio Nanetti found checking mite populations besides a real treatment is unreliable. It is many factors making the results uncertain. Why beekeepers want to do this anyway is to get an idea when it’s time to treat against the mite.
If you do an oxalic dribble, or trickling, you make a real treatment. And that’s okey with me, if you choose to do that. Before making a real treatment the most reliable mite test is said to be alcohol washing like with the bee shaker described in this blog. The sugar shaker might do well for others. According to findings in USA described by Dennis van Engelsdorp those beekeepers that checked mite populations with alcohol wash, thus keeping track of the mite population had the lowest winter losses, of those beekeepers treating regularely.
John Harbo and his collegues at Baton Rouge lab found in the early 1990:s when they took help of a statistican to find out that checking mite population increase during a period of time was not a good way of testing mite resistance. That’s why they finally ended up checking infertility of the mites, which finally became the VSH method. (Information from Harbo)
That’s also one of the resons I don’t count mites. I check for virus problems in the hive before treating. The easiest virus and the one most common when mites are becoming many is Deformed Wing Virus (DWV). Maybe that’s too late normally to save the colony. I don’t know. But fortunately I don’t have ”normal” bees. Also a reason for me not counting mites, but looking for DWV, is that I want my bee stock to develop strong varroa (and virus) resistance.
Hello Erik,
First, you seem to be moving away from cell size as a mite controll. This is logical, as you were on 4.9 when Varroa arrived in Sweeden ad killed so many colonies.
Second, I thought that when DWV, or any virus is seen, the damage is done, and treatment is usually too late. This is usually at the end of Summer when healthy nurse bee are critical for Winter survival.
Hello Gregory
Oh no, I don’t have data to convince me that small cells are not beneficial for bees in fighting mites. On the contrary. But there are so many things to write about, and so many things that influence bees. Small cells are no doubt more natural, at least in the brood area. And natural selection is always favoring survival and prosperity (fitness).
Yes, I suspected that most experiences are in line with that damage is done and treatment is too late when you see DWV-wings late in season (maybe also in spring). And this has been the case partly also with my bees when this appears very late in the season. But for my Elgon bees on small cells and in our climate treatment in late August after discovery of DWV-wings is mostly not too late. And after using this selection method now since 2009 the use of thymol has decreased and the number of candidates as breeders have increased. Today a colony has to have been treatment free the last two years before the current year to bee in question as breeder.
But if you don’t have so many colonies and want to be sure that your bees are going to survive the winter, I fully understand if you choose to treat regularly, best some time before winter bees are made.
The best alternative before choosing a breeder (if you find enough many mites) is to make a VSH-test as I have written about in other blogposts.
Best regards/Erik
I would like to comment on Marco’s comment about Prof. Nanetti. He cited him by saying that only oxalic acid treatment for the whole stock if I understand correctly is precise in telling the varroa load.
And he comment about the sugar method by saying that’s to variable as humidty and temperature count.
I guess there is some truth in it, because oxalic acid seems to get rid of most of the mites (95% is the number I heard, when correctly applied). Sugar dust seems to be not as efficient, therefore if applied for varroa control you have to repeat several times. However, the sugar has one big advantage. You don’t kill the bees and as treatment you don’t harm neither the bees nor the brood. Whereas oxalic acid treatment can be applied only early in winter only, when there is no brood. So it is not suited during main season or you apply for some bees similar to alcohol treatment.
Secondly, Marco can you recall the conditions of treatment (e.g. humidity and temperature) that are more beneficial or effective for the sugar dust method? And can you quantify the amount of mites released, when changing one parameter. That allows a direct comparison between the different parameters and even methods, which would be good. Otherwise it is to nebulous, as I for instance don’t know does the sugar method remove only 30% of mites or 60% or 75%?
Last comment, if you always apply the same method (e.g. less efficient as sugar dust) and let’s say the measurement variation is similar, then you should get an idea, even if you take 300 bees from the same location (let’s say from frames) about varroa development within the year. From a practical perspective – Erik you call it the art of beekeeping – that might be sufficient to get an idea about the varroa situation in your hive to answer the questions: a) when do I have to treat and b) is the hive a good breeder.
Regards,
Rüdiger
Concerning Nanetti, it might be the case that he proposes to use a real trickling with oxalic acid whenever you want to know the varroa situation in the colony, even if it is a lot of brood in the colony. If used for that purpose you take a big sample of bees for the “test”, the whole colony (without the brood). It is of course a much bigger sample and more reliable because of that and you get more mites out from the sample (maybe 95 % of the phoretic mites). And you get a quite good treatment at the same time. With unselected bees for varroa resistance (“normal” bees) a figure often given is that one third of the mites are phoretic and two thirds are in the brood. So you kill about one third of the total amount of the mites. It’s quite good as a treatment but not at all enough for a real treatment.
But is it a good test in the meaning that you can compare different colonies concerning mite density in the colony, or compared with the same colony a month or so earlier to get an idea of the increase of mite population? (Some use this as a tool for testing the degree of varroa resistance.) Not really, without further calculations. You have to get a figure for the number of bees treated with oxalic.
Next question is if calculating the increase or the amount of mites is a good tool telling mite resistance. According to the statistician working with Harbo, Harris et al in the 1990th it is not. But we are of course free to choose our methods and follow our ideas.
Sugar dust method both for checking the mite infestation in a colony and for treating against mites differ depending on weather conditions and how you do it. In the sugar Sugar Shaker post I mentioned that Randy Oliver managed to get 65-70% of the mites from a sample of bees. Macedo 80-90%. Probably you can get even lower.
But if you do it the same way, you can use the method for checking what’s happening in your colonies and you can learn in your situation when it’s time to take action of some kind.
If I used the sugar shaker method, which I don’t, I would use it for checking when it’s time to treat. I would not use it as part of a method to find breeders. I use other methods that I find successful, which I mentioned in the original post for these comments.
Spring is here finally and many colonies had their main cleansing flight, the first for but a few, Sunday 9. Yes! Another interesting season!