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I have used an oxalic vaporizer for several years for varroa control. I have also lost more than 50% of my hives over that period. I have never seen a drop-off of dead varroa after vapor treatment like I did with Apigard and other chemical treatments. Has anyone who uses oxalic vapor seen where it actually killed mites and had a drop-off on a tray under the screened bottom board? Has anyone had a problem losing queens when using oxalic acid vapor? Thanks, Jim
 

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yes, the white board is a way to determine mite drop after a successful OAV treatment.

If you are using OAV, and not getting a mite drop, and then confirming a high mite load with a mite wash, the application or dose is not correct.

Use a bare minimum of 2 grams for a double deep. That's what the label states, but many beekeepers use 3-4g.

Be sure to use a band heater vaporizer.

Queens can get lost, but it's quite rare.
 

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There are pictures here on the forum of drops of a thousand. I think one username was Glock. I have not seen really large drops but I havent allowed mite load to get high.

Colony losses at that high a percentage suggests there may be other factors at play such as not early enough treatements and/or calling it good. too early in the fall and having a resurgence later from robbing etc.
There has been increasing awareness of the need to get mites under control and keep them there during the time of brooding several rounds of winter bees. It takes several months after the last of the virus vectoring mites have been dispatched for the virus levels to drop to tolerable levels. You are not home free yet when the last mite dies!

There are 20 some different viruses affecting bees and their presence and level can vary greatly from one locality to another and from year to year. Nosema is another wildcard.

There has not been much in the way of reports of anything more than minor mortality that were not also suspect of having improperly mixed dribbles or someone having sourced "wood bleach" that may have been lye or bleach based rather than oxalic acid.
 

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There are pictures here on the forum of drops of a thousand. I think one username was Glock. I have not seen really large drops but I havent allowed mite load to get high.

Colony losses at that high a percentage suggests there may be other factors at play such as not early enough treatements and/or calling it good. too early in the fall and having a resurgence later from robbing etc.
There has been increasing awareness of the need to get mites under control and keep them there during the time of brooding several rounds of winter bees. It takes several months after the last of the virus vectoring mites have been dispatched for the virus levels to drop to tolerable levels. You are not home free yet when the last mite dies!

There are 20 some different viruses affecting bees and their presence and level can vary greatly from one locality to another and from year to year. Nosema is another wildcard.

There has not been much in the way of reports of anything more than minor mortality that were not also suspect of having improperly mixed dribbles or someone having sourced "wood bleach" that may have been lye or bleach based rather than oxalic acid.
If you are using OA vapor only to control mites you should be treating around 12 to 14 times a year, 3 weeks in summer with 2 treatments a week the same again in September and then 2 treatments when broodless November and December.
 

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I see mite drops on the drawer, I use Johno’s pro vap. This past Fall there were a lot of mites even with using Formic Pro and OxV. I did not do counts this year, too many hives and heavy supers to move around for me. I heard that many other beekeepers noticed higher than usual mite loads too. I will not use Formic Pro again, there were queen problems with it, so I thought I would try Apivar this Spring instead of Autumn.
 

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I started using OA treatment several years ago and early on it worked well with only a couple of hive loss over the winter. This late Fall I treated all my 16 hives in three stages ( per Provap directions) to kill stages of mites. Hives where all very strong up until February. Weather here in CT turned for the worse and I lost them all. At first I thought it was starvation but after further investigation my alcohol wash mite counts are 13 to 18 per 300 bees Average. Is it possible the OA was bad or expired ( shelf life)? It was Wood Bleach and kept in a sealed container. Any thoughts on what could have caused this? Appreciate any input.
 

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I started using OA treatment several years ago and early on it worked well with only a couple of hive loss over the winter. This late Fall I treated all my 16 hives in three stages ( per Provap directions) to kill stages of mites. Hives where all very strong up until February. Weather here in CT turned for the worse and I lost them all. At first I thought it was starvation but after further investigation my alcohol wash mite counts are 13 to 18 per 300 bees Average. Is it possible the OA was bad or expired ( shelf life)? It was Wood Bleach and kept in a sealed container. Any thoughts on what could have caused this? Appreciate any input.
"This late Fall I treated all my 16 hives in three stages" I think this is where the problem starts. Too late to get the required 2-3 rounds of brood raised in mite free conditions to get "Fat winter bees".
 

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Here is my timeline.
3 treatment cycle on all hives ended 6/7/20
Fall 3 treatment cycle ended 9/26/20
Hives wrapped and sugar boards placed for winter.
The weather was on and off warm and really did not get cold until February. I don’t think I could have done anymore treatments. I have heard some people do OA treatments on a regular basis during the year
 

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Not enough. What were your counts in September? Did you treat after that or take counts after that? I’m in Massachusetts, lost 2, bees didn’t have mites but had lots of signs of mite vectored viruses.
 

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My 2 C. I started with bees in 2015 and used Apivar by label spring (end Winter) and Fall. Lost 50% for two years each winter. Wash showed 2-4% mites in fall. Then I started with a pan style vaporizer and the losses did not change, but the whole treatment was agonizing, time wise. 2019 I build my first band heater VAP and treated 7x4 days apart with 3 gram on double deeps from the back. No loss in 19/20 and no loss 20/21. Today we had 16°C, 61°F and I started my first treatment and will check my bottom board on the day of the next treatment, Monday. The bees where out like mad today, calm and super sunny. I treat in the evening when everyone is home. The treatment per hive takes 20 seconds. My motto: the right 'puff' makes the difference!
 

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Mapleone;

If your treatment were three at seven day intervals that would not be sufficient if there is a high mite load in surrounding bees. Too many mites are drifting in between individual vaporizations and certainly between series. I dont give breaks between series and shorten the intervals down to 3 or 4 days. It is a bit different story when they definitely have no brood.

See Johno's post #4
 

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If your treatment were three at seven day intervals that would not be sufficient if there is a high mite load in surrounding bees. Too many mites are drifting in between individual vaporizations and certainly between series. I dont give breaks between series and shorten the intervals down to 3 or 4 days. It is a bit different story when they definitely have no brood.

See Johno's post #4
Well Frank, you mean me? I treat 7 times, 4 days apart, so 28 days total!
 

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Well Frank, you mean me? I treat 7 times, 4 days apart, so 28 days total!
Sorry Joerg; You posted while I was replying to Mapleone. I agree 100% with your program. I edited my post to show who I was directing it too.
 

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Sweet. Life is good, the bees are flying! I know we will pay for it, way to early for Alberta's Banana Belt.
 

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I have used an oxalic vaporizer for several years for varroa control. I have also lost more than 50% of my hives over that period. I have never seen a drop-off of dead varroa after vapor treatment like I did with Apigard and other chemical treatments. Has anyone who uses oxalic vapor seen where it actually killed mites and had a drop-off on a tray under the screened bottom board? Has anyone had a problem losing queens when using oxalic acid vapor? Thanks, Jim
You are aware that multiple oxalic treatments are required to properly control. your mite infestation? It only kills those mites exposed in the colony. Those in capped cells reproducing are unaffected. Mites have a 13 day breeding cycle so personally I treat three times every fifth or sixth day. That way I believe I catch the vast majority of the mites out in the open during one of those treatments. I also am always ready during the broodless portion of the winter to treat on a warm day when the bees are flying or at least loosely clustered. Another opportunity to decimate mites not safe in capped cells. I like Apiguard too! I rotate a treatment of it into my strong hives every other year. It is too rough on weak colonies so I do not use it on nucs or small splits IMO. You are right to be suspicious of mites in your winter losses. Sugar rolls or alcohol washes are also important in knowing what your mite levels are. I am a wimp and do not like killing bees to test so I use the sugar roll. Now that we can treat with OA when supers are on, It will be more important to regularly check mite levels and do on the spot treatments. At least that is my plan.
 

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Mapleone, I use OAV and treat often. August 1st is the important date to start with in order to get healthy winter bees. Every 4-6 days in August... healthy winter bees make healthy bees for spring.
 

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I did an alcohol wash right around 9/5 and the majority of the hives showed zero mites. Only a couple had max of 3 mites per 300 bees. Therefore I thought I would play it safe and treat all 3 treatments spread over 7 days. Is it safe to assume going forward I should do the following:
1. Test regularly and treat accordingly
2. August 1st start 3 treatment process and do every 3 to 4 days ( not 7 days)
3. Treat again as late as possible prior to Winter close up say late September weather permitting of course

Now that it appears to be safe to use OA with Honey supers on it could be more effective.
Last can someone explain the " Fat Bee statement"
 

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I did an alcohol wash right around 9/5 and the majority of the hives showed zero mites. Only a couple had max of 3 mites per 300 bees. Therefore I thought I would play it safe and treat all 3 treatments spread over 7 days. Is it safe to assume going forward I should do the following:
1. Test regularly and treat accordingly
2. August 1st start 3 treatment process and do every 3 to 4 days ( not 7 days)
3. Treat again as late as possible prior to Winter close up say late September weather permitting of course

Now that it appears to be safe to use OA with Honey supers on it could be more effective.
Last can someone explain the " Fat Bee statement"
The fat bee concept seems to be that bees who have not nursed or foraged have a much much larger fat body which is the source for the first rounds of brood raised in the spring. They can survive for ~ 5 months whereas bees which have nursed and foraged time out at about 6 weeks of age. Hopefully these winter bees will also harbor a much lower level of virus.

On OA treatments; it seems that the shorter time interval between treatments eliminates the number of mites that slip through the 7 day period. Mite falls seem to indicate that the main effective time is the first 3 days after vaporization and it tapers off quickly. The next 4 days may allow mites to emerge and re enter cells unscathed. ( second and third time females can re enter cells immediately without a blood meal on a bee.)

When you shorten the time between treatments you must add more treatments to extend the time to cover the same 21 day period. Personally I keep repeating 3 or 4 day interval treatments till the dead drop level is near zero. No breaks between to allow a senseless recovery.
 
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