Varroa drop rate

[justsmith]

Bit worryed about one of my hives it's getting around 3 varroa mite drop a day right now, by the looks of the wax droping they have brood on 5 frames (nat std size). My other have a much lower drop rate but they was in a colder place over winter.

Should i look at a course of treatment for them?

 

[B+.]

Should i look at a course of treatment for them?

According to the attached chart, your bees are already "threatened" but, you should remember, mites die all of the time. How reliable is your information?

 

[B+.]

Bit worryed about one of my hives it's getting around 3 varroa mite drop a day right now, by the looks of the wax droping they have brood on 5 frames (nat std size). My other have a much lower drop rate but they was in a colder place over winter.

The wax dropping will only tell you where the bees are, not where there is brood. They are probably eating stores and the queen will start to lay a few eggs now.
The natural mite drop gives you an idea of the phoretic mites (those travelling on the adult bee rather than those that are reproducing in the sealed cells, of which there will be few at this time of year). It is really only reliable when there is very little, if any, sealed brood. For these reasons it is used at the start of the season to give an initial infestation level.
As the season progresses, and there is more sealed brood for the mites to reproduce in, the natural mite drop is less reliable so we have to turn to other methods (e.g. http://coloss.org/beebook/II/varroa/3/1/2). The chart that I posted earlier uses these methods but starts around May when it is possible to collect samples from the bees themselves. After a few points on the graph, you can extend a line and predict where the infestation level is likely to be at any point in the year. This makes it quite a useful tool.

 

[Tremyfro]

That's a useful chart...thanks I've saved it. I was wondering also about colonies which are not treated for varroa....what their chart would look like. I know you don't treat....so does the varroa level climb into the threatened area in the same way? In other words is the prediction the same?

 

[Erichalfbee]

After a few points on the graph, you can extend a line and predict where the infestation level is likely to be at any point in the year. This makes it quite a useful tool.

Thanks B+ I shall use these and give copies to my local BKA along with Beekeeping-equipment's last sugar roll kit that I bought them

 

[B+.]

That's a useful chart...thanks I've saved it. I was wondering also about colonies which are not treated for varroa....what their chart would look like. I know you don't treat....so does the varroa level climb into the threatened area in the same way? In other words is the prediction the same?

No. The chart is a good guide, but. there is always variation in nature (even between sister queens mated to drones from the same (4a) mother. That variation comes from the random selection of 16 from the, (2a) queens, 32 chromosomes and from natural mutations which can occur (mutation isn't always bad....its also evolution). In selective breeding, we are looking to identify those which exhibit these desirable characteristics and propagate them.
Effectively, the gradient of the line will be different. The flatter the line, the more desirable the colony is for varroa management since the rate of population growth is less.

One thing I would add is, don't take the readings too close together. If you take them at least 3 weeks apart, you won't be testing the same "batch" of workers and you will get less error in the line. You could do lots of readings every week (if you really wanted to) but, you then have to draw a line of best fit. Its more hassle than its worth and adds nothing to the accuracy

 

[B+.]

Thanks B+ I shall use these and give copies to my local BKA along with Beekeeping-equipment's last sugar roll kit that I bought them

You're very welcome. All I did was translate the chart and spend a few minutes amending the pdf. The thanks should go to the Hessen association in Germany. Its their chart.

 

[Erichalfbee]

oooops double post

 

[charlievictorbravo]

Don't forget that the number of mites on the vertical axis of the B+ chart is not the drop for the whole colony - it is the number of mites found after sugar rolling 10g of bees. If you're counting natural drop of a colony on a monitoring board, you'll probably have to use calculator or chart 54 on page 33 in Managing Varroa

CVB

 

[B+.]

Don't forget that the number of mites on the vertical axis of the B+ chart is not the drop for the whole colony - it is the number of mites found after sugar rolling 10g of bees. If you're counting natural drop of a colony on a monitoring board, you'll probably have to use calculator or chart 54 on page 33 in

Think about what is happening and when you would perform these tests:
The natural mite drop is performed early in the spring when you wouldn't want to open up a colony. It is probably going to be too cold and you don't want to risk chilling any young larvae the colony may have. It measures phoretic mites that are naturally dying or being groomed off the workers. They fall through the open mesh floor and are collected on a board under the OMF. If you don't have something sticky on the board, they may become the meal of any microscopic creatures (or even ants, etc) that live under the colony. You are only interested in the dark red mites which are the adult females as these could have laid eggs which would become the next generation of mites. You are not interested in lighter coloured mites (immature females or males) as they cannot survive outside of the cell.The purpose of this test is only to give you a number which represents the initial infestation of the colony and other tests are better later in the season.
As the weather improves, and the colony expands, you may wish to monitor the growth in the population. This can be done with various tests (i.e. sugar roll, soapy water wash, etc). They are best done with adult workers from the supers to avoid the risk of killing the queen by accident. Also, there is evidence to show that the population is more uniform (consistent for measuring purposes) in the supers furthest away from the brood nest. This may seem somewhat counter-intuitive because varroa mites prefer to parasitize young nurse bees because they actively feed the young brood in cells that the varroa wants to reproduce in. However, bees will fly away from the colony and reduce the infestation in the colony. By taking them from the supers, you are also smoothing out any peaks and troughs caused by mites emerging from the cells at a certain point in time. Effectively, its an average...not an exact number, as this will change all of the time.
Other tests may include pin-killed or freeze-killed (with liquid nitrogen) brood, but, this shouldn't be confused with varroa monitoring. These tests are concerned with the rate at which worker bees are able to detect and remove dead pupa. They test "hygienic" behavior. I perform these tests during the first week of July but follow them up with repeats about 3 weeks later. The hygiene will be expressed as a percentage of the number of cells completely emptied within a given period (8-12 hrs for pin-killed brood and 24 hours for frozen brood).
Colonies which express the highest hygiene percentage can be tested further (i.e. hygiene is considered a pre-selection test for VSH testing because of the amount of effort involved in these tests). I intend to begin VSH testing for the first time this August as I now have stock that should express high VSH. Basically, this involves uncapping 30 pupae (at least 7 days post capping - http://www.beekeepingforum.co.uk/album.php?albumid=751&pictureid=3789) and counting the number of reproducing / non-reproducing mites in the cells. VSH is also expressed as a percentage.

 

[Eyeman]

Here at Purdue we have developed bees that groom themselves free of mites and bite them resulting in death, another root behavioral trait. Colonies that have a higher proportion of mites on their 24hr sticky boards tend to be the best mite-biters, in addition we observe fewer mites on the adult population!

Perhaps we should be looking at those fallen mites under the microscope?