Friday, 20 April 2018

Start of the Season

This week, the weather suddenly changed.  Gone was the drizzle and April showers, and suddenly we're in glorious sunshine, with temperatures as high as 24°C.  Finally, on Wednesday, I got to open the hives!

There were basically three tasks for the day:

  • If the colony in the double-height nucleus is strong enough, split the colony.
  • In the hives, move the honey supers from underneath the brood boxes (my preferred winter configuration) to the top, with the queen excluder between (this is the summer configuration).
  • Check for queens, and the overall health and well-being of the colonies.

So, let's step through how the year's first inspection went:

The Nucleus

Part of the reason for splitting the double-height nucleus was so that I could move the blue nuc (which has a fixed floor, and is slightly more portable) over to Sydney Gardens, where the colony will move into the ZEST hive.  But first I had to check all was well.

The bees were busy - a good sign.  I found the queen (Elena) in the top half of the double-height nuc (the brown nucleus), so I swapped the frame she was on into the blue nuc, and moved another frame the other way.  This left the blue nuc with bees, stores (honey), brood (capped, uncapped and eggs) and a laying queen.  All good.

The brown nuc now has 5 frames of bees, stores, brood and eggs, but no queen.  This is no problem at all - the bees will start to make queen cells, and within 4 weeks I should have a laying queen in the brown nuc.  Task completed!

Hive #1

Fairly busy - of the 11 frames in the brood box, all had bees on them, and there were six frames of brood.  the queen (Laura) gave me the run-around, and I had to go through the brood box twice before I eventually found her.  The colony looked healthy and busy.  I put the brood box back at the bottom of the hive, then the queen excluder with the super on top, and closed the hive.  Task completed!

Hive #2

I was actually a little surprised that there are still bees in this hive, because of the outbreak of Sacbrood that I observed in the autumn.  But they are still hanging on in there, even though it's now quite a small colony.  Finding the queen (Maria) was easy.  But there is a problem - the brood.  There were only three frames of brood, and it all looked like this:

Bad brood

The dome-shaped cappings are characteristic - this is all drone brood.  And yet I have a queen who is less than a year old;  normally I wouldn't expect a queen to start failing until she's in her third season at least.  Has she become sick in some way, and her spermatheca is no longer working?  She is still laying eggs (I saw some), so why are they all unfertilised (male) drones?

Then, on another frame, I spotted a queen cell, with royal jelly in it, and a roughly 3-day old embryo.  And while putting this post together, I took a closer look at the photo above and saw this:

Emergency Queen Cell?

That looks to me like an emergency queen cell.  This suggests that one of two things is going on - either:
  1. The queen is still laying a tiny number of worker eggs, and when she does they are getting "promoted" to queens.  Or...
  2. The workers are creating queen cells, because they know the queen is failing, but they have no female eggs to work with.  So they are raising drones in queen cells.  I had a nucleus a few years ago where this happened - the workers will realise there is something wrong with the queen cells a couple of days after they're capped, and then destroy the (drone) larva and the cell.
So, I'm hoping it's [1], and the colony will soon get a new queen.  Otherwise, I will have to intervene (possibly by donating a queen cell from the nucleus, assuming that they make more than one).

The next inspection day looks like Saturday 28th April, so until then I will be crossing my fingers and hoping the bees sort things out for themselves.

Friday, 13 April 2018

Organic Acids in Beekeeping - Part 2 - Formic Acid

Science warning: this post contains actual science. You have been warned...

Formic Acid molecule
(Wikimedia Commons, Public Domain)
In part 1, I covered the basic chemistry of organic acids.  Though you could say that my explanation was the opposite of basic...  (If there are any chemists reading - yes, that was a little in-joke just for you).

Last time we covered oxalic acid, which is used in the winter.  Beekeeping is usually done in the spring, summer and autumn, which means that we need a Varroa treatment that can be used during the warmer months.  Enter formic acid.

Like oxalic acid, formic acid is an organic acid.  But unlike oxalic acid, formic acid contains a carbon-hydrogen bond - which means that it meets the (not entirely accurate) definition of an organic molecule.

And, also like oxalic acid, formic acid exhibits the behaviour of a Brønsted acid.  Formic acid is a carboxylic acid, which means it can donate one proton (positively-charged hydrogen nucleus).  This then makes the formic acid molecule negatively charged, a state known as the conjugate base.  When in this negatively charged state, formic acid is called formate.

If you're still awake, let's move on to where formic acid is found in nature.  One place where you will definitely have encountered it is as a component of the stinging hairs on stinging nettles.  It is also a component of the venom of ant stings.  In evolutionary terms, ants are fairly close cousins of honey bees.  And yet, bee stings don't contain formic acid.  Weird.

So, our interest in formic acid in beekeeping is not in the bees themselves.  Rather, it is because formic acid is useful as a weapon against the Varroa mite.  Formic acid is an acaricide, which is a chemical agent that kills ticks and mites.  The specific mode of action is that it acts on the mitochondria in the cells of the Varroa mite.  Mitochondria are found in the cells of all animals, and they generate energy through aerobic respiration.  There are different processes for doing this (I will spare you the details), but they result in the production of adenosine triphosphate (ATP), which is the molecule that is used for energy transfer throughout the body.

The processes all rely on a very clever bit of biochemistry called an electron transport chain.  This is a sequence of enzymes that receive, and then pass along electrons (negatively charged particles) along the chain.  The end of the chain is negatively charged (because of the electrons), which creates an electrical gradient across a membrane in the mitochondrion.  This causes protons (those positively-charged hydrogen nuclei again) to flow across the membrane from the neutrally charged side to the negatively charged side.  And this proton flow provides the energy for an enzyme called ATP synthase to create ATP.

At the end of the electron transport chain, but before we get to ATP, is an enzyme called cytochrome c oxidase.  As with each of the enzymes in the chain, the job of cytochrome c oxidase is to receive electrons from further up the chain and pass them along.  But formic acid inhibits the action of cytochrome c oxidase.  This interrupts the electron transport chain, which prevents the proton flow and stops the production of ATP.  Without ATP, the Varroa mite has no means of transferring energy round its body, so it dies.

So, does formic acid affect ATP production in honey bees?  Well, actually - yes.  But the effect isn't as severe.  Some bees die in the first few days of treatment, and there is a risk (though less than a 5% chance) of losing the queen.  But these are acceptable losses and risks, when compared the the more significant problems - including colony loss - that can be caused when the number of Varroa mites in the hive gets too high.

I usually apply a formic acid treatment once a year, normally a week after I've harvested the honey.  It comes in the form of a gel which takes about a week to evaporate.  I don't particularly like doing it, but needs must.  And the bees don't like it either, but I suppose taking your medicine is no fun, is it?