The beginning of this week was fine enough to get beekeeping jobs done before the temperature dropped below 10 degrees C again. Cynthia was keen to get her sugar shake varroa tests done, and they are much easier to do with an assistant. I was lured into Nairn to help by the offer of tea and cream-filled apple turnovers.
Luckily there was only one varroa in our sample of 300 bees and the bees were returned to the super none the worse for shaking. Rather than explain the sugar shake test, I’m going to share a paper that I wrote on a comparison of 2 methods of assessing varroa levels in colonies. You can see the equipment that we used and how we did it.
Soaking vs. Shaking –Trying Out a New Varroa Testing Tool and Comparing with Sugar Shake Method by Ann Chilcott, Scottish Expert Beemaster. A version of this article first appeared in The Scottish Beekeeper Vol 94, No 10 October 2017.
I was interested in evaluating Véto-pharma’s product Varroa easyCheck, and its comparison with the sugar shake method of assessing levels of varroa in a colony, so I carried out a small research project.
Monitoring varroa drop through an open mesh floor (OMF) onto a sticky board is a useful technique if carried out over a 7- day period, and when a daily average drop is calculated. The varroa calculator on Bee Base will advise when treatment should be carried out based on these results. However, unless the OMF is clean the varroa drop may be obstructed by debris so the methods that I describe are more accurate and give a snap-shot of varroa infestation on a particular day.
It was previously believed that varroa compromised honey bee immunity and health by feeding on the haemolymph and transmitting viruses via this method. However, Samuel Ramsey, whilst a PhD student at Maryland University, USA, discovered recently that varroa feed mainly on the honey bee fat bodies, preferring sites between the 2nd and 3rd abdominal plates which is more serious than we previously thought and also compromises bee nutrition.
Fat bodies are specialised organs that function in a similar way to our livers. They are suspended in the bee’s haemocel (abdominal body cavity) and have immediated contact with the haemolymph (bee blood). They are a bee’s principle organ of metabolism, functioning in many aspects of a bee’s physiology, including energy storage, detoxification, and synthesising important proteins called vitellogenin (responsible for stimulating egg production). They are also essential in maintaining a healthy immune system. Varroa infestations compromise all these areas and so bees are even more vulnerable to infection and ill health.
Bee health can be further compromised by careless beekeeping, poor weather and lack of forage, and exposure to pesticides—both agricultural and beekeeping chemicals.
We have even more reason now to control varroa infestations because we also know that many viruses are transmitted by varroa. It is now no longer appropriate for beekeepers to tolerate such high levels of varroa as previously accepted due to changes in mite and viral dynamics.
With so many new beekeeping products appearing on the market, I was curious to see if Varroa easyCheck was more accurate than a sugar shake test so I tested 7 colonies in the summer of 2017 using both methods on each colony at the same time.
Equipment required for my tests
Both methods involved collecting two samples of 300 live bees from each of the brood boxes of the seven chosen colonies. I wanted to collect mainly nurse bees so I chose frames that had a lot of unsealed brood. I shook each chosen frame into a large dry plastic bucket and swirled it around to keep the bees at the bottom while I scooped up 300 of them in a measuring container—a half cup measure used in baking holds that number of bees.
The easyCheck Test
The easyCheck container has 2 measuring lines inside the removable basket. The lower mark measures 200 bees, and the upper mark 300. The instructions suggest running the mesh basket up the frame to collect and remove bees but, having tried this, I found it easier and quicker to and obtain all my samples by shaking bees into the bucket first.
This method involves killing the sample of bees in alcohol. 5% alcohol will quickly kill bees and winter–strength car windscreen washer fluid is recommended by Véto-pharma so I used this.
Following instructions, I poured fluid into the container up to the bottom line marked on the outside. This line was difficult to see so I enhanced it by tracing a black marker pen over it. Then I poured in the sample of 300 bees inverting the container and swirling to keep the bees down before I opened container again and topped up the fluid to the top marker line. I then swirled the bees round in the container for 60 seconds using my stop-watch to time this. After this time the mites could be seen at the bottom of the container and counted. The fluid was strained through mesh and reused, and the varroa count was confirmed.
The Sugar Shake Method
I collected my sample of 300 bees, as above, and placed in glass jar with mesh lid. I swirled the jar around to keep the bees on the bottom as I opened the lid to insert 2 heaped tablespoons of icing sugar. I rotated the jar a few times to fluff up the bees and cover them in icing sugar. I left them for two minutes to get all hot and bothered inside the jar which made the varroa too hot also so they crawled out from under the bee’s tergites. If you see varroa on bees in your hive you can be sure that there is a heavy infestation because they are usually hidden away feasting on fat bodies.
I then shook the jar onto a plate (you need a solid plate as disposable ones can blow away at the crucial moment—believe me) so that the icing sugar fell out onto the plate. I shook each sample for the recommended 90 seconds and noticed that the mites usually started falling after the first minute.
The bees were then released onto the top bars and they went down into the frames fairly quickly. I was not stung during the study.
Using the water spray, I sprayed the sugar on the plate to reveal varroa mites which I then counted before cleaning plate for next test.
|Mite count: Sugar Shake
|Mite count: Alcohol Wash
The Student unpaired t-test was performed and it was found that P=0.42
Note: P = the probability of getting the difference observed by chance. If P< 0.05 then this would indicate that the difference found was significant (not due simply to chance).
The small difference in the average mite counts occurred by chance, such as testing different frames, hence I found no significant difference in these two methods of varroa testing. Nevertheless, the two methods have their differences in how they are affect the bees and the beekeeper.
With the sugar shake method, the bees are alive at the end, which I like. However, this method takes longer to perform than the alcohol wash, and it is messier and stickier.
With the easyCheck method, the bees are dead at the end. But it is quicker, less messy, and requires less equipment .
While I shall probably continue to use the sugar shake test on my own few colonies, bee farmers and others may prefer using the quicker easyCheck test. Some beekeepers may find that they can easily use the mesh basket to collect bees which will make the test even easier to perform.
However, if you capture the queen by mistake you might be sorry.
Treatment Threshold: If there are over 2% varroa in your sample of 300 bees then treatment is required before August. In August treatment is recommended above 3%.