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making oxalic strips
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<blockquote data-quote="NatureAlley" data-source="post: 12915" data-attributes="member: 91"><p>In this whole story there are (at least) two key players: oxalic acid and the degree of infestation with mites. OA is in my opinion not a very strong acaricide, partly because it is a contact poison and does not readily evaporate from strips. Both have to be critically considered and a treatment can only be successful if it is understood how to combine observations and knowledge about these two in the best possible way.</p><p></p><p>The physical state of the OA is considered an important factor by some, but not all. I have too little experience to judge but the "Otto" strips I have used for 5 years always worked well. Never lost a hive to Varroa. In the hands of most of those who contributed to this interesting discussion both crystalline and liquid OA seem to be able to do the trick... but not always. Humidity? Perhaps, hive humidity fluctuates with the RH outside the hive. It is not easy to control, but whether it is proven to be a decisive factor, I am not sure.</p><p></p><p>It is not my intention to stir up the OA discussion, but would like to draw attention to the other key player: the number and even more, the concentration of phoretic mites (mites per volume if you like) at a certain moment in time and the envisioned growth rate of this number as depending on the amount of infested brood cells. If over a certain period of time the increase in numbers of mites surpasses the decrease by the action of whatever poison (supplemented with natural mite deaths), it is .. "Houston, we have a problem!"</p><p></p><p>An otherwise healthy but small hive with just a few frames of brood and a few mites dropping on the sticky board still means a relatively high number of mites per colony size. If you would ONLY look at this and extrapolate to a bigger hive, then such a colony maybe less vulnerable with that number of mites dropping at that moment. The incertainty (among many more, no doubt) is that the degree of infestation in the brood is not always known. Especially in the early stages where it really matters and things can get out of hand (i.e. pass the point of no return) pretty quickly.</p><p></p><p>As a retired biologist and hobbyist beekeeper I can afford and really enjoy spending a good amount of time with my colonies. An qualitative estimate of phoretic mite numbers is made by evaluating mite drop on a sticky board (every 24 hrs around 1st of Feb and 1st of Aug). Combined with colony size and how much brood there is it helps determining when it is time to put the strips in. For an average colony (sic!) the cut off I use is 5 mites dropping in 24 hrs. This is not dogma, please, just describing what I do and so far with reasonable success.</p><p></p><p>So before treating (which is based on number of mites dropping and colony/brood strength) I concentrate the colonies as much as possible, that way the chance for mites to get some OA on them is enhanced. Also making sure the strips are located where an encounter is favourable. And in case of doubt, I tell myself: better safe than sorry, put them in earlier rather than too late.</p><p></p><p>BTW: dropped mites are almost never evenly distributed over the sticky board. Some areas (corresponding to the front and back of the hive) are having way more mites than the more central areas. I have always been concerned that this might influence mite counts with alcohol or sugar shakes. But that opens a different can of worms.</p><p></p><p>Disclaimer: just my experience.</p></blockquote><p></p>
[QUOTE="NatureAlley, post: 12915, member: 91"] In this whole story there are (at least) two key players: oxalic acid and the degree of infestation with mites. OA is in my opinion not a very strong acaricide, partly because it is a contact poison and does not readily evaporate from strips. Both have to be critically considered and a treatment can only be successful if it is understood how to combine observations and knowledge about these two in the best possible way. The physical state of the OA is considered an important factor by some, but not all. I have too little experience to judge but the "Otto" strips I have used for 5 years always worked well. Never lost a hive to Varroa. In the hands of most of those who contributed to this interesting discussion both crystalline and liquid OA seem to be able to do the trick... but not always. Humidity? Perhaps, hive humidity fluctuates with the RH outside the hive. It is not easy to control, but whether it is proven to be a decisive factor, I am not sure. It is not my intention to stir up the OA discussion, but would like to draw attention to the other key player: the number and even more, the concentration of phoretic mites (mites per volume if you like) at a certain moment in time and the envisioned growth rate of this number as depending on the amount of infested brood cells. If over a certain period of time the increase in numbers of mites surpasses the decrease by the action of whatever poison (supplemented with natural mite deaths), it is .. "Houston, we have a problem!" An otherwise healthy but small hive with just a few frames of brood and a few mites dropping on the sticky board still means a relatively high number of mites per colony size. If you would ONLY look at this and extrapolate to a bigger hive, then such a colony maybe less vulnerable with that number of mites dropping at that moment. The incertainty (among many more, no doubt) is that the degree of infestation in the brood is not always known. Especially in the early stages where it really matters and things can get out of hand (i.e. pass the point of no return) pretty quickly. As a retired biologist and hobbyist beekeeper I can afford and really enjoy spending a good amount of time with my colonies. An qualitative estimate of phoretic mite numbers is made by evaluating mite drop on a sticky board (every 24 hrs around 1st of Feb and 1st of Aug). Combined with colony size and how much brood there is it helps determining when it is time to put the strips in. For an average colony (sic!) the cut off I use is 5 mites dropping in 24 hrs. This is not dogma, please, just describing what I do and so far with reasonable success. So before treating (which is based on number of mites dropping and colony/brood strength) I concentrate the colonies as much as possible, that way the chance for mites to get some OA on them is enhanced. Also making sure the strips are located where an encounter is favourable. And in case of doubt, I tell myself: better safe than sorry, put them in earlier rather than too late. BTW: dropped mites are almost never evenly distributed over the sticky board. Some areas (corresponding to the front and back of the hive) are having way more mites than the more central areas. I have always been concerned that this might influence mite counts with alcohol or sugar shakes. But that opens a different can of worms. Disclaimer: just my experience. [/QUOTE]
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