25 Apr 2015

Small hive beetle - the clear and present danger

Small hive beetles (SHB) had arrived in Victoria.  Actually they did arrive some time ago but they get more visible over time.

SHB seem to be the gift of Olympics 2000.  First detected in 2001 around Newcastle, it since spread over NSW and Qld.  It favours warm and moist climate so it was slow to move south, but now it is in Victoria.  If you see inside or outside a hive a black beetle the size of a ladybird - this is it.

When SHB overwhelm a hive, they makes the bee colony abscond, looking for a better place.  In USA it is called "September swarming", as it usually happens in the second part of the year.  On 13 April I have received a call to remove a bee swarm.  I could not believe it - bees DO NOT swarm in Melbourne in April, but the caller sounded knowledgeable and was insistent.  I went there and here it was - a proper swarm on a roof, with scouts etc.  SHB are the only explanation I can think of.

USA beekeepers from southern states claim that for them SHB are worse than varroa.

I have no direct experience with SHB, but I saw them already in a few hives.  No losses as yet. Here is the summary of a search on available SHB info:

1. SHB can easily enter hives, bees cannot stop them even if they try.  Indeed they do their best but to no avail.

2. Once beetles are in, bees have no natural way of removing them.  They cannot kill them, they cannot kick them out.  Conclusion - beetle numbers in hives tend to grow over time with no natural limiting factor in sight.  This is really scary!!!

3. Bees chase the beetles, try to contain them in tight spots ("beetle jails") and keep them there.  They can do it, but then the beetles have sneaky ways to make bees feed them.  Keeping beetles in check keeps a number of bees away from useful work and may be a feasible strategy only up to a point.

4. Beetles themselves do not cause any damage but if a number of them lay eggs, the larvae quickly overwhelm the hive and turn it into a slimy stinking mess.

5. Hive inspections and manipulations cause general chaos and let beetles get out of jails.  This often allows them to lay eggs and to bring down the hive.  Another possible trigger for a catastrophe is if the number of beetles inside is simply too high for bees to control.

SHB are claimed to be of little concern to beekeeping in Africa, where they came from.  African bees are known to have the tendency to abscond at a drop of a hat - maybe this is their way to shake off beetles and limit SHB damage?

 These are the known strategies to fight SHB or at least minimize damage:

- beetle trapping outside hives.  Traps resemble wasp traps.

- denial of hive entry by hive design, with or without trapping, see www.beetlejail.com.  Also alternative designs may be possible, taking advantage of differences in bee and beetle size and legs length.

- beetle trapping at the hive entrance.  For current designs refer Mrs. Google.

- beetle trapping inside the hive.  Numerous traps are on the market, again refer Mrs. Google.  Traps require periodical emptying.  Some traps allow emptying from outside, some require hive opening.  Overall efficacy of traps is unknown at this time.  Traps are unlikely to get all the beetles and the question is - to what degree the beetles not trapped are capable of bringing a hive down.

Possible additional strategies:

- hive designs that leave no room for beetles to hide.  Langstroth hives seem to be a beetle paradise with numerous small tight spots.

- floor mesh with openings large enough for beetles to be pushed out.  If it works, this may allow bees to remove beetles and bees indeed try to do it.  However, it may work only if beetles cannot enter a hive from below.  Beetles can land on a horizontal surface and most likely on a vertical one as well, but surely not upside down.  It is unclear whether they could walk upside down on a reasonably smooth surface.  Possibly metal or plastic may not offer enough for beetles to hold on to so a bottom mesh say #6 (3.5 mm opening) with metal/plastic collar may just do the job.

The above is just a summary of what I could gather so far.  The April swarm really made me worry.  Please comment if you can.  If you have more information, please send a message.  Let's tackle the problem jointly.

Andrew


2 comments:

JohnandJean said...

Our hive is in the Hunter Valley. SHB is present but seems to be in manageable proportions.

We use an external trap mounted in the floor (Beetltra) The bees dump the SHB into the trap filled with Lime or diatomaceous earth. We have also tried to make sure the hive has no hiding spaces e.g. rounded corners and no holes in the frames.

The SHB seem to find their way into the trap under normal conditions. But before the hive is opened the trap is refreshed. The SHB go to the bottom of the hive as you work your way into the hive and into the trap. Like a Spring cleaning.

Have tried detergent in the trap but it goes smelly within days.

Having the hive in a sunny position and a strong colony also seemed to help in control.

We have used similar internal traps but they are a nuisance when you have gloves.

Anonymous said...

With respect, isn't it a big assumption to think that the swarm was due to SHB with no evidence of SHB? Bees swarm at the "wrong" time of the year for lots of reasons. I had a very late swarm due to the colony being disturbed because of building works.
I think i've noticed SHB in my colonies, but only a few. I guess time will tell if they get out of hand.