April is the month when it should start to get busy in the apiary. The first hive inspections can be made as soon as it is warm enough to open the hive without danger of chilling the young brood. The old beekeeper's saying that 'if the Flowering Currant is out then it is time to do the spring inspection' is not as reliable as it used to be. New varieties of Ribes sanguineum now flower much earlier. A better test for a suitable temperature is to roll up your sleeves when outside. If that feels comfortably warm then it should be warm enough to make an inspection.

In April fields of oilseed rape should be in flower and beekeepers need to be ready. OSR is the first of the crops that can give a surplus of honey if the weather conditions are right. In other areas bees will be busy collecting nectar and pollen from early fruit trees such as pears, plums, cherries, damsons and apples. There should be a succession of blossom now as April showers bring forth all the May flowers. Many spring flowers provide good forage for bees from the lowly dandelions to bee-friendly trees such as Sycamore and Horse Chestnut.

You may need to put supers on your hives before it is warm enough to do any of your spring inspections. An early flow of nectar can often take beekeepers by surprise. It is very important that the bees have plenty of available space in which to store this early rush of incoming nectar. If they haven't got super room, they will store the nectar in the brood area and this will restrict the amount of space the queen has available to lay her eggs. This congestion will trigger the swarm impulse and yes, bees do swarm in April sometimes.

April should be full of promise for the year ahead, but it isn't always like that. April is also the time that many beekeepers open up their hives for the first inspection and find out, to their horror, that their bees are dead. It often comes as a complete shock because bees may have been seen coming and going from the hive giving the impression that all was well inside. But these bees may just have been robber bees looking to see if there was any food worth stealing.

This time last year, reports were coming in of a much higher rate of colony losses than is usually expected. Generally it has been accepted that, for various reasons, 1 in every 10 colonies won't make it through the winter. However, over the last seven years or so, records show that the percentage of winter losses has been gradually creeping upwards.

If you find that your bees have died, it is important to find out why they died before you use the hive again. So close up the hive entrance until you have time to deal with it properly.

At a time like this it is helpful if you can ask your mentor or another experienced beekeeper for help. Some causes are easy to identify such as starvation.

When this is the reason, as well as a pile of dead bees on the floorboard, many bees will have died with their heads in the cells searching for food. Obviously there is nothing contagious about starvation so a quick clean is all that is needed before the hive can be repopulated.

If you didn't bother to fix a mouseguard to the hive entrance then combs that are gnawed away and the unmistakable smell of mouse urine will be the give away signs that a mouse has taken advantage of your hospitality. The damaged frames are best replaced as bees do not like the smell of mice and the floorboard may need a good scrub or scorching to make it more welcoming for the next residents.

If the front of the hive and the frames are heavily soiled with bee diarrhoea, then that is more serious as it shows that the bees were suffering from dysentery. Dysentery is not a disease but it is an indication that there is or was a major problem. There can be various causes; a likely one is fermentation of the winter stores in the hive. It used to be thought that dysentery was a sign that the bees have Nosema, a gut parasite. It is now known that this is not so, but if the bees do have Nosema then it will be spread more rapidly if the bees also have dysentery. The inside of the hive will probably be a mess. If the frames are covered in bee poo, they are best replaced. Cleaning and sterilizing these contaminated frames for re-use is laborious work. It is quicker and more hygienic to make up new frames with foundation than to recycle the old ones. They make good firelighters. The inside of the hive will need sterilising using a blow lamp too. Then it will be safe for new occupants.

Sometimes though, the cause of death of a colony is not so obvious and this is often the case with varroa and varroa related problems such as viruses. Few beekeepers have had much experience with viruses yet and even mentors can be occasionally stumped for an explanation.

Many beekeepers do not have mentors, and even more do not belong to a beekeeping association of any kind. There is no obligation to do so of course, but it is always useful to have someone to go to for up-to-date advice.

Fortunately there are people who can give help when it comes to giving expert advice and you don't have to be a member of any beekeeping association to get this benefit.

The National Bee Unit (NBU), based in North Yorkshire, has a team Bee Inspectors that cover England and Wales. Officially known as the Bee Health Inspection and Advisory Service for England and Wales, it has more than forty experienced practical beekeepers who are trained in the recognition of bee diseases. The Bee Inspectors don't just deal with outbreaks of foulbrood; they also provide assistance to beekeepers on a wide range of bee health issues and give advice on good apiary management including varroa control. Check out http://beebase.csl.gov.uk to find out more.

After particularly bad bee losses in England and Wales in Spring 2007 the NBU responded by securing funding to investigate all reported colony losses. Inspectors collected over 700 samples from dead or dying colonies and these were tested for a range of drugs, pesticides and pathogens (things that cause diseases).

A particularly interesting discovery was that the virus linked with Colony Collapse Disorder in the United States, IAPV (Israeli acute paralysis virus) was not found in any of the colonies tested here. That's the good news. The bad news is that they did confirm cases of Nosema ceranae, a newly arrived Asian variant of the more familiar pathogen Nosema apis.

The most commonly found virus was DWV (Deformed wing virus). As its name suggests the bees' wings do not develop properly. Worker bees must fly from the hive to collect food and water, but with deformed wings they just drop to the ground, crawl around and die. With little or no food coming into the hive the rest of the colony soon dies too.

This virus and many others are linked with varroa mite infestations. Research has shown that varroa mites suppress honey bee immunity and can transfer virus particles as they bite the bees to feed.

When there seems to be no obvious cause for the death of a colony, then varroa and an associated virus are very likely candidates.

So, when you come to do your hive inspections in April and May, if you find that your bees are dead and particularly if your colony losses are considerable, then close up the hives, block up the entrances and call the Bee Inspector for your area. The same applies if you experience an unexpected and sudden colony loss during the summer.

Most beekeepers do not realise that they can request a visit from one of the Bee Inspectors and that the service is still free. All you have to do is ask. In fact the Bee Inspectors would like you to do this. It is only by recording losses, making visits and taking samples that they can build up a proper picture of what is really happening to our bee colonies.