I thought I would do a page about some of the pests and diseases Bees have to live with. The page will be updated from time to time, especially as I am still a complete novice. All the information will be taken from what I've read in either books or on the net, or from what I've heard at Beekeeper meetings.
Varroa is a small mite visible to the naked eye, approx 1–1.8 mm long and 1.5–2 mm wide and reddish brown in colour. The full name for this mite is Varroa Destructor! It can only reproduce in a honey bee colony and does so by crawling into uncapped cells with developing larvae inside; it then lays about 6 eggs in the cell (5 female and 1 male) who will develop in the cell and leave when the developed Bee departs the cell. At this point the newly developed adult mites will pass onto other Bees starting the cycle again. The mites feed on the Bees "blood" or hemolymph and by doing so weaken the bee and possibly pass on other infections. Due to how quick the mite can reproduce it appears to be one of the major factors that is worrying beekeepers at the moment. I have read about several different treatments for varroa. Some of the varroa treatments are chemical based and seem to have a good success rate however there is strong argument against treating with chemicals. The main point I see is that by treating we are encouraging hives that are unable to fend off varroa naturally to survive and pass on their genes and if not treated effectively then the mites may develop resistance to treatments, making them harder still to get rid of. In my opinion a better treatment is sugar dusting, which is a mechanical method of removing them. This works by dusting the Bees with powdered sugar; this then makes the Bees groom them selves and dislodge the mites. This method makes more sense to me in the long run as the Bees will be dealing with the problem themselves and in future generations this behaviour could be bred into their genes giving them better defence. Another thing that is said to help is to get a varroa floor in the hive. This is a grate floor big enough for the mites to drop through, causing them to die as they can't climb back, but small enough so the Bees can't get through. Usually there will be a inspection tray underneath so you can count how many mites are falling. It has the added advantage of providing more ventilation for the hive.
Nosema is a single celled fungal infection that lives in the gut of the Bee. To find out for sure if your Bees have this disease then they need to be looked at with a high powered microscope by someone with a microscopy certificate. Nosema is passed from Bee to Bee through their excrement when Bees do their house cleaning and because of this worker Bees are effected more than drones and queens. Bees infected with this could develop dysentery and a common sign is yellow streaks of excrement out side the hive and in extreme cases also inside the hive. The disease shortens the Bees lifespan by inhibiting the function of the gut and preventing digestion of pollen. Again there is a chemical way of treating for Nosema which involves mixing a substance known as Fumidil B with sugar syrup and dripping onto frames in the hive; this then gets into the Bees system as they clean up the mess made and treats the problem. I have also read that keeping the hive well ventilated has a very good effect of keeping the hive free from Nosema in the first place!
European and American Foulbrood
European Foulbrood and American Foulbrood (EFB and AFB) are diseases caused by bacteria within the hive; EFB being the lesser threat to Bees though still considered harmful. Both diseases should be reported to DEFRA if you live in the UK. Though they sound like they are from either Europe or America, this is not the case and their names are derived from where they where discovered first. Prior to been classified as two separate diseases they were just known as foulbrood.
Is mainly a threat to Bees if already stressed by other factors. I doesn't damage the Bees directly but as the bacteria lives in the Bee larva's gut, EFB can cause starvation by eating the larva's food; This is mainly only a issue if there is a food shortage. Some of the symptoms include erratic brood pattern, twisted larvae with visible creamy/white guts through the body wall, sour smell to the hive, larvae that looks melted down almost like wax. If you think you have EFB then close your hive and contact your local Bee inspector immediately. Also make sure all your equipment is disinfected thoroughly though it is good practise to make sure equipment is cleaned regularly anyway.
American foulbrood can be devastating to a hive an quite often will result in the hive having to be destroyed. It is spread by spores that develop in capped brood, which die inside their cell. When the dead larva is removed it can spread the spores throughout the entire hive. An infected larva can contain millions of spores so infection can spread alarmingly fast. Symptoms include sealed brood with sunken caps, putrid odor, dead larva lying flat on cell wall, dead brood is soft and ropey when a matchstick or similar is inserted. Once infected the disease can become dormant for many years, which is one reason for avoiding used equipment if not sure of it's past. As with EFB, you should contact your local Bee inspector straight away and seal the hive to stop more hives being affected.