Category: pest and disease

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The problem with waps is they do like to feed on bees, larvae and honey

Yellow jackets can be very persistent in wanting to enter the hive, but the bees are usually a little ahead of them in building up their numbers and are able to defend the hive entrance.

If the hive is a little weaker or you find many wasps are easily gaining access to the hive (I wouldn't worry about the odd occasional wasp briefly sneaking in), you might consider reducing the entrance down to make it easier for the bees to defend.

 

In situations where it feels like a hive is really under attack, or it becomes impossible to perform inspections without large gangs of wasps appearing, wasp traps can gradually reduce the wasp numbers around your hive. I'm not proud of this, and dislike using them, so it's only something I've used reluctantly in situations where I felt it would prevent bees from suffering.

The trap in the video above is simply a water bottle top cut off and placed back into the bottle upside-down. This creates a funnel entrance into the center of the bottle. Any wasp that enters will have difficulty finding this entrance again. As the transparent bottle lets light in through the sides, this is where they search for an exit.

The bottle can be baited with a fermenting sugar or meat so wasps will be attracted but not bees.

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What a mouse in a hive looks like

Once a mouse enters a hive they typically chew out the bottom corner of a few frames to make space. They will then bring in nest material. This is a view from the bottom of the box:

Mouse nest viewed from bottom of hive box.

You will probably see evidence of the nest on the bottom board as well.

If you are using a screened bottom board, there is a good chance you can determine if you have a mouse just by looking at the tray under the screen for mouse droppings and fallen nest material.

Signs of the mouse nest under the screened bottom board

It's said that mice will often move out as it starts to warm up and the bees become more active. If not, the bees can attack the mouse and you may find the remains (possibly propolized) within the hive.

Aside from the damage to comb, mice are also problematic in the pungent stench of urine that they leave behind in the hive.

Evidence a shrew has been around the hive

Pygmy ShrewPhoto by: minipixel / CC: Attribution-NonCommercial-NoDerivs License

Shrew's don't nest in the hive, but they do leave behind signs of their visit. You may find droppings that are slightly different than those of mice. There will also be bee carcasses. Shrews eat the bee innards and leave behind a hollow exoskeleton. Most often they get at the innards via removing the head of the bee.

Shrew eaten bee carcass

If you do successfully exclude shrews from your hive, you may still find these decapitated dead bees outside the hive. It seems like they will feed on either the dead bees taken out by the undertaker bees, or those bees that leave the hive to die. Shrews are small but they need to eat frequently, over the course of a winter they can take a significant toll on the bee population.

Shrew and Mouse excluders

Generally the standard wooden entrance reducer is not sufficient for excluding mice, there are many stories of the wood being chewed away to enlarge the opening.

For a few years I've seen good results from both simply adding nails to standard entrance reducers and cutting myself thicker wooden entrance reducers from 1.5" wide wood. Was I just lucky?

Entrance reducer made from a wide piece of wood.

It's very popular to make or purchase metal excluders with holes drilled into them.

Installing mouse exclosuresPhoto by: Tie Guy II / CC: Attribution-NonCommercial-ShareAlike License

The use of hardware cloth as a mouse excluder is not uncommon either.

Hardware cloth to keep mice out of a beehive

Size of entrance required to exclude mice and shrews

The openings beekeepers use for a mouse excluder are sized between 1/4" (6.35mm) and 1/2" (12.7mm), with commercial products typically using a 3/8" (9.25mm) diameter circle. 

There's a fine line between leaving enough space for adequate ventillation, allowing bees to remove the dead, and to bring pollen in during the early spring, while still securely preventing mice from entering. There's lots of debate as to whether a 1/2" gap is sufficient to keep the mice out versus 1/4" making it too difficult for the bees to do everything they want to do.

As far as the 1/2" camp goes, there are some beekeepers who claim to have not had a problem in 40 years. There's also some references from mouse owners using 1/2" mesh cages for adults (but many in the mouse world do seem to cite needing 1/4"). Are their regional differences, like species of mice, as well as how likely it is to find smaller, younger mice at the time of winterizing, your hive?

I haven't found as much info out there about shrews. There is reference online to Fletcher Colpitts, Chief Apiary Inspector of New Brunswick citing the use of both 1/4 and 3/8" spacing for winter and then switching to 1/2" once there is spring pollen. Anecdotally, I can say I am finding beheaded hollowed out bees this year outside, but not inside of the hive in the photo above which is using 1/2" mesh with the vertical opening height made slightly smaller as it overlaps the wood of the hive. I take that to be a positive sign.

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American foulbrood (AFB) is the most devastating honeybee disease.

AFB kills the infected colony. It's high virulence also means it can easily be spread to other colonies within foraging distance.

AFB infected comb showing perforated brood cells and a spoty brood pattern
Spotty brood pattern on a comb infected with AFB. Via Flickr.

Not only do you loose your bees, all comb and frames must be destroyed to prevent further infections. Even a small outbreak can be both heart breaking and expensive.

Identifying American foulbrood

The following video provides quick overview of:

  • the matchstick or 'ropiness' test
  • AFB scales
  • brood pattern symptoms

Being able to confidently diagnose AFB is critical. Spotting AFB in the early stages allows you to take immediate action and reduce the severity of impact to your apiary.

More information and illustrations can be found on the Ontario Ministry of Agriculture and Rural Affairs web site.

American foulbrood scale on comb
Infected comb with AFB scale and perforated brood cells. Via Flickr.

Responding to an AFB infection

Protocols for dealing with AFB vary vary slightly by region. Typically one must report the disease and burn infected equipment. Some areas do allow you to keep hive boxes as well as outer and inner covers if you scorch them with a blow torch to kill spores. You might even be able to save your comb if you are willing to pay to have them irradiated.

A few jurisdictions do permit you to try and save your bees using the shake method. While people have reported success with this method, areas that permit shaking bees with AFB almost always have a higher overall infection rate.

AFB scale
American foul brood scale removed from cell with toothpick. Via Flickr

Preventing American foulbrood

As a very basic precaution, it's useful to scorch hive tools before opening different hives. This can be done either with a propane torch or by placing your tool in a smoker. You want to see the propolis on your tool boil.

There is also some suggestion that poor nutrition can leave bees more susceptible to AFB. For example, a lack of lactic acid bacteria (LAB) found in honeybee's gut may diminish their ability to ward off the disease. In one experiment LAB levels were charted based on bee feed type (see pg. 15).

In some parts of the world antibiotics are fed to bees to mitigate the risk of contracting AFB. Unfortunately, this has given rise to strains of American foulbrood developing resistance to particular antibiotics.

A few other tips to help limit the spread of disease can be found here.

Link

The influence of brood comb cell size on Varroa destructor in Africanized honey bee colonies

Study by Giancarlo A. Piccirillo and D. De Jong of São Paulo's entemology department which found a high correlation between cell size and mite reproduction in africanized honey bee hives.

Link

Dennis vanEnglesdorp October 13th, 2012 - YouTube

Dennis vanEnglesdorp speaks to the New Jersey Beekeepers Association about different diseases and issues facing be health and offers some stats on treatments.

The second part is a question and answer session in which the pesticide question gets a fair bit of attention.

Link

Beekeeping by Rotation System from Celle Germany

A little while back I put out some requests on the web for ideas on how to keep hive numbers steady for locations where there is a limited amount of space for reproduction and it was suggested to me that I look at the Dutch Aalster method, or the Rotation method from Celle, Germany.

What little english info I able to find on these approaches suggests it is really a method for disease/pest control that is designed to keep productive populations during flows while creating breaks in the brood cycle and cycling out old comb from the brood nest. Though many variations seem to exist, the most detailed information on the approach comes in the form of this IWF documentary.

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I first noticed bees with deformed wings virus(DWV) crawling around in front of one of our stronger hives in the late summer of last year.

We treated in the fall, and by spring symptoms had dissapeared. It was the strongest of our twenty hives this spring and we had to split it to try and keep it from swarming. By late summer(Sept. 1st) I once again started noticing bees with deformed wings. From this point in the season on, anytime I looked, I was able to find at least one if not a handful of damaged bees crawling around in the area directly in front of this one hive.

varroa mite on bee with DWVPhoto by: Shawn Caza / CC: Attribution-NonCommercial-ShareAlike License

Notice the mite on the bee in the above photo. Mites help transmit DWV and are the cause of more severe infections as they harbour a much higher concentration of the virus than is found in the bees themselves.

Bees with deformed wings are expelled from the hive and typically have a life span under 48 hours. Seeing large amounts of DWV is a clear indicator a hive is suffering from a serious varroa problem.

Bees with DWV may also have really stubby short abdomens. In some cases I see the short abdomens without necessarily seeing visibly deformed wings. I believe these stubby bees with healthy looking wings, are also incapable of flight.

Bees with DWV and short stubby abdomens.

 

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Sugar dusting bees is a non-chemical, relatively harmless approach for dealing with varroa mites. The concept is that covering the bees with sugar will make things slippery for the mites and stimulate grooming behaviour in bees.

It's widely accepted that sugar dusting will successfully knock down a portion of the phoretic mites, that is those mites riding on the adult bees, but not those reproducing under capped brood. As such, this approach is most useful to employ during a queenless period after the old queens brood had emerged but before brood from the new queen is capped.

Generally sugar dusting is viewed as just one component of an Integrated pest management system, useful for keeping numbers down, but one shouldn't expect it to function as a magic bullet that will solve all your mite problems.

The effect upon the hive is immediate and obvious. Bees run for cover and once sugared, stop whatever else they were doing and proceed to clean the sugar off. I've typically tried this using about 1 cup of powdered sugar per deep brood box. In my experience, most of the mite drop will happen in the first 15 minutes. This photo is an example of what can be pulled out of the bottom of the hive in 15 minutes.

In the first hour I'm usually able to recover about 1/3 of the sugar from the bottom board. This technique works best in tandem with a screened bottom board, as it knocks off the mites but doesn't kill them. You can slide something like cardboard into the entrance of a solid bottom board when sugar dusting so the mite can be easily removed after the drop.

The main drawback to sugar dusting is that the bees do appear to devote a fair bit of energy cleaning out the sugar. The following video shows a colony actively in clean-up mode after sugar dusting. The video was shot at the end of November, there was little forage available this time of year, as such the hive entrance had been very quite prior to dusting.

Randy Oliver at scientificbeekeeping.com has experimented a fair bit about this form of mite control. His three part series is some of the most useful information I've been able to dig up on the subject. He's found weekly sugar dusting can slow mite reproduction, but it might not knock them back enough by itself. In the end his experiemnts may have raised as many questions as they answered. If nothing else, his experiments suggest that full colony sugar dusting might be one of the best ways of assessing a colonies infestation rate:

"The take-home message is that the results of this series of tests lead me to question the reliability of either natural mite fall or the alcohol wash (or ether roll) as monitors of mite infestation level! It appears to me that a whole-colony mite drop accelerated by sugar dust (or other mite dislodging agent) is likely the most accurate field-practical way to determine a colony’s mite level."