🐝 Pests, Diseases and What Controls Them

There is a short list of bee diseases that the world takes seriously enough to track across borders. Knowing that list, and knowing who to telephone about it, is the first thing a commercial beekeeper should learn. It comes before mites and before beetles, because getting this wrong can cost you not only your colonies but your right to sell.

The World Organisation for Animal Health, WOAH, lists six bee diseases and infestations in its Terrestrial Animal Health Code. Member countries are obligated to report their occurrence. The six are:

1. Acarapisosis of honey bees, caused by the tracheal mite Acarapis woodi.
2. American foulbrood of honey bees, caused by the bacterium Paenibacillus larvae.
3. European foulbrood of honey bees, caused by the bacterium Melissococcus plutonius.
4. Small hive beetle infestation, Aethina tumida.
5. Tropilaelaps infestation of honey bees.
6. Varroosis of honey bees, caused by Varroa species.

Learn those six names. They are the diseases that close borders, stop consignments and trigger inspections.

Now the qualification that matters more than the list itself, and that is misunderstood constantly. The WOAH list is an obligation on countries to report to WOAH. It is not, by itself, a law telling you what to do. Whether an individual beekeeper is legally obliged to report a suspected case, who they must report it to, and what happens afterwards, is set by national law and differs completely between countries. Some African countries have a formal apiary inspection service. Many do not. This course cannot tell you which yours is, and it will not pretend to.

So what does the course teach instead? Find out before you need to know. Today, while all your colonies are healthy and you are calm, find out who your national veterinary or agriculture authority is, whether they require notification of bee disease, and what telephone number reaches them. Write it on the front page of your record book. The day you open a hive and find sunken greasy cappings and a foul smell is not the day to start looking for a phone number.

And this rule, which is absolute: never destroy or move a suspect colony before asking. There are two reasons. The first is that burning is sometimes exactly right and sometimes wrong, and you cannot tell which without a diagnosis. The second is that in a country with an inspection service, destroying evidence of a notifiable disease can itself be an offence, and moving a suspect colony spreads the disease you were trying to escape.

Two diseases most African beekeepers actually meet are not on the list. Nosema is not WOAH-listed. Wax moth is not WOAH-listed. That does not mean they are unimportant. Wax moth destroys more African equipment than anything else on this page. It means only that they are not internationally notifiable, so no border closes over them. Do not confuse the seriousness of a disease to you with its status in international trade law.

Notice something else about the list. Two of the six are the pests you will meet most: small hive beetle, which is a native African insect, and varroosis. Tropilaelaps is a mite of Asian origin that has been spreading, and acarapisosis is a tracheal mite you cannot see without a microscope. American and European foulbrood are the two brood diseases, and they are the ones that make second-hand equipment dangerous.

Why does this list justify a whole lesson? Because the single most expensive mistake in African beekeeping is not a mite. It is moving bees and equipment. Cross-border movement of bees is how Varroa, small hive beetle and Tropilaelaps have travelled the world. Movement of bees is regulated in most countries and is often licensed or prohibited. Do not import bees or queens across a border. Do not buy a second-hand hive from someone who cannot tell you what happened to the colony that was in it. Local bees are adapted to local forage and local disease, and transported bees abscond anyway.

The practical position for a small beekeeper is simple. Know the six names. Know the number to call. Ask before you act. Never move comb or bees you cannot vouch for.

Varroa destructor is a mite about 1.1 mm wide and 1.6 mm long, flat, brown, and visible to the naked eye if you know where to look. It has changed beekeeping everywhere it has arrived. Understanding one fact about it explains every control method there is.

That fact is this: Varroa reproduces only inside a capped brood cell. The mated female mite enters a cell containing a larva just before the bees cap it, waits roughly 60 to 70 hours, and then lays. Over her life she may complete up to seven reproductive cycles and lay around 30 eggs. A worker cell stays capped for 12 days. A drone cell stays capped longer, because a drone emerges on day 24 against a worker's day 21. So drone brood is the mite's preferred nursery, because it gives her more time.

Everything follows from that.

• A contact treatment cannot reach a mite under a capping. Any treatment must either span a whole brood cycle or be applied when there is no brood.
• Removing capped drone brood removes mites with it. That is a control that needs no chemical at all. Be honest that the efficacy of drone-brood removal was not confirmed from a trial for this course; it follows from the biology rather than from a measured result.
• Making a split creates a broodless interval, which is a natural gap in the mite's breeding.

The damage Varroa does is mostly not the feeding. It is the viruses. Varroa carries deformed wing virus, black queen cell virus, sacbrood, Kashmir bee virus, acute and chronic bee paralysis viruses, out of the 18 known honey bee viruses. Deformed wing virus is what actually kills the colony. Bees with crumpled, useless wings crawling at the hive entrance are the classic sign, and by the time you see many of them the colony is in trouble.

Now the part that matters most for an African apiary: you must measure, not guess.

There are two field methods.

Alcohol wash. Collect about 300 adult bees from brood frames. Submerge them in alcohol. Swirl vigorously for at least one minute. Strain through mesh and count the mites that come out. The bees die; that is the cost of an accurate count.

Powdered sugar shake. Put the bees in a jar with about two tablespoons of powdered sugar. Shake vigorously for one minute. Wait three to five minutes. Invert the jar over a white surface and collect the mites. The bees live.

Either way you get two numbers: mites counted and bees sampled. Divide the first by the second and multiply by 100. That is your infestation percentage. With 300 bees, 9 mites is 3 percent.

United States guidance sets thresholds by colony phase: below about 1 percent when dormant, below about 2 percent during population increase, peak and decline, with prompt treatment above 1 percent dormant, above 2 to 3 percent during increase and decline, and above 3 percent at peak. Read that as an example of how a threshold is written, not as your rule. Those are United States thresholds for European-derived bees, and their applicability to African bees is unestablished. This course does not claim it.

Here is why that caveat is not a small one. African honey bee populations are described in the review literature as able to resist diseases and novel parasites, and Kenyan bees have been reported to show Varroa-specific hygienic behaviour. Many African colonies live with Varroa without treatment. Mite numbers peak soon after adult and brood populations peak.

So the teaching rule is: monitor before you treat. Do not import the European assumption that routine treatment is necessary. Routine prophylactic treatment of a tolerant population wastes money, puts acaricide residues into your honey and breeds resistant mites. Wash a sample, count, and decide.

On treatment, this course is deliberately silent. It names no acaricide, no dose, no temperature window and no withdrawal period. Which products are legally registered for use in bees, at what dose, and with what withdrawal before harvest, is decided by your national veterinary medicines or pesticide regulatory authority. A product legal in one country is illegal in its neighbour. Using a registered product in a way inconsistent with its label is an offence. And never apply anything with honey supers on, because residues in honey are a food-safety failure that will close an export market.

What you may always do, lawfully, anywhere: remove drone brood, split to create a broodless period, and requeen from hygienic stock.

Aethina tumida, the small hive beetle, is native to sub-Saharan Africa. This is your insect. It was detected in the United States in 1996 and has spread worldwide since, and where it has arrived as a stranger it has been devastating. In its native range it behaves differently: it is normally a secondary pest of weak colonies, policed by strong ones.

That difference is the whole lesson. The beetle is not primarily a chemistry problem in Africa. It is a colony strength problem.

Know what you are looking at. The adult is 5 to 7 mm long and 3 to 4.5 mm wide, dark, hard-shelled and fast. When you lift a comb, adult beetles run away from the light, down into cracks and corners. That running behaviour is the field sign. The eggs are tiny, about 1.4 mm by 0.26 mm, laid in cracks and crevices. Larvae grow from 1.3 mm to about 1 cm and have small legs at the front, which distinguishes them from wax moth larvae.

The life cycle, and why it is fast in your climate. Eggs hatch in 1 to 6 days, typically within 3. Larval development averages about two weeks, with a range of 8 to 29 days depending on food and temperature; one source gives 10 to 14 days. Then the larvae leave the hive and burrow into the soil to pupate. Pupation takes 2 to 12 weeks depending on soil temperature and moisture, with another source giving 15 to 100 days. They pupate in chambers 1 to 20 cm deep. Adults live up to 12 months in the field and 16 months in the laboratory. A single female lays about 1,000 eggs in her life, possibly up to 2,000. Fewer eggs hatch below 50 percent relative humidity.

Now the damage. Larvae tunnel through comb, feeding on honey, pollen and brood. Their feeding causes fermentation of stored honey, and the honey turns to a running, frothy, foul-smelling mess. Beekeepers call it slime-out. It causes severe comb damage and often full structural collapse of the nest. And adults can cause colonies to abscond entirely. That is a documented, direct link between this beetle and the biggest cause of colony loss in African apiaries.

Control. Read the order carefully, because it is not the order most people expect.

First, keep colonies strong. Serious damage is generally inflicted on weak colonies. A strong colony patrols its combs, corners the beetles and holds them prisoner. A weak one cannot. So everything that keeps a colony strong is beetle control: requeening, controlling other pests, selecting hygienic stock, feeding when a dearth threatens starvation.

Second, do not give a colony more comb than it can cover. This is the single most useful practical rule in this whole module and it costs nothing. Unattended comb is beetle habitat. In a top-bar hive, use a follower board and keep the colony on the number of bars it can actually hold.

Third, traps. Oil-filled or bait-filled in-hive traps and fabric entanglement traps are used. Any trap bait or in-hive chemical is a matter for your national authority; this course names no product.

Fourth, the soil. Diatomaceous earth or slaked lime spread around the hive works by tearing the cuticle of larvae and causing desiccation. Here is where the biology pays off: most larvae tunnel into the soil less than 180 cm from the colony. So you only need to treat the ground immediately around the hive, not the whole apiary. That derivation from the pupation radius is what turns a general recommendation into an affordable one.

Fifth, harvest and process promptly. The worst slime-outs happen in harvested comb left standing in a shed. A bucket of crushed comb waiting three days is a beetle nursery. Get honey strained and comb rendered.

One more thing to notice. Small hive beetle likes humidity: fewer eggs hatch below 50 percent relative humidity. In a dry season your beetle pressure falls; in a humid coastal climate it does not. Learn your own pattern and record it.

The honest summary: in Africa the small hive beetle is usually a symptom. If it is destroying your colonies, ask what made those colonies weak first.

If you ask African beekeepers what destroyed their equipment, more will say wax moth than anything else. The damage caused by Galleria mellonella larvae is described as severe in tropical and sub-tropical regions, and it is a significant threat across Africa and Asia. This is the pest you will actually fight.

The life cycle first, because one number in it explains everything.

Eggs hatch in 3 to 30 days. Females lay them in clusters of 50 to 150 in cracks and crevices inside the hive, which is why a hive with split boards and loose joints is a moth farm. The larval stage runs from 28 days up to 6 months before pupation. Pupation takes 1 to 9 weeks. Adults live about 21 days for males and about 12 days for females. There are 4 to 6 generations a year.

And here is the number that matters: the optimum development temperature is 29 to 33 degrees Celsius.

That is African ambient temperature. In Europe wax moth is a summer problem that stops in winter. Across most of Africa the moth is inside its optimum range for much or all of the year. Teach yourself to think of it as a continuous pressure, not a season.

What the damage looks like. The larvae tunnel through the comb, chewing along and through cell walls and leaving silk-lined tunnels behind them. Then comes the webbing, masses of it, binding combs together. Under it you find dark frass like coarse pepper. In an infested piece of stored comb, the whole thing eventually becomes a grey mass of web and droppings with the wax eaten out of it.

There is a specific and cruel form of damage worth naming: galleriasis. The moth silk runs across the face of the brood comb, and emerging young bees get entangled in it. They cannot free themselves and they starve in the cell mouth. Infestation causes colony loss, absconding, and reduction in the size of migratory swarms. Once again a pest links straight back to the absconding problem that defines African beekeeping.

Now control, and be realistic about which options you actually have.

Strong colonies defend their own comb. Wax moth is overwhelmingly a stored-comb problem and a weak-colony problem. The bees patrol the comb face and remove eggs and small larvae. Kenyan practice states the rule plainly: remove old combs that the bees are unable to cover in time of food scarcity. That is the same rule as for small hive beetle, and it is free.

Freezing works. Minus 7 to minus 15 degrees Celsius for 2 to 4.5 hours interrupts development. Note the practical problem honestly: most African smallholders have no freezer. Teach the method because someone with access to a cold store or an ice plant can use it, but do not present it as the answer.

Bacillus thuringiensis, Bt, is a biological control. Combs are dipped in or sprayed with a Bt spore suspension. In field trials, efficacy declined after the initial season. Bt registration for hive use varies by country, so it is a matter for your national authority before you buy any.

Which leaves management, and that is genuinely the realistic African control:

• Do not store empty comb. This is the single biggest change most beekeepers can make. Comb sitting in a shed is comb being eaten.
• Render surplus comb into wax promptly. A block of clean wax cannot be eaten by moth. A stack of comb can. This is the reason the wax lesson and the pest lesson belong together.
• Keep colonies strong and populous.
• Do not leave harvested comb standing. Process it the same day where you can.
• Keep the hive itself in good repair. Cracks and crevices are exactly where the 50 to 150 egg clusters are laid.
• Store any comb you truly must keep in the light and in a draught, in a stack with air moving between the boxes, rather than sealed warm and dark.

One more thing. Wax moth on a dead colony's comb is not the cause of death, it is the undertaker. If you find a hive full of webbing and no bees, the question to ask is what killed the colony first: starvation in a dearth, absconding, disease, or a queen failure six weeks earlier. The moth simply moved into an empty house.

Brood diseases are different from pests. A beetle you can see running. A brood disease you have to read from the brood itself, and getting it wrong in either direction is expensive.

American foulbrood, caused by the bacterium Paenibacillus larvae, is the most serious brood disease in world beekeeping. Here is the fact that makes it so serious: the spores stay dormant in colonies or in used equipment for 70 or more years. A single dried scale in a cell may contain perhaps 100 million spores. That is not a disease you clean up. That is a disease that contaminates equipment permanently.

The larvae die after the cell is capped, in the last two days of the larval stage or the first two days of the pupal stage. So the signs are in capped brood.

What to look for:

• An irregular, spotty brood pattern where healthy solid brood should be.
• Cappings that are sunken, dark, greasy and perforated, as if something inside pulled them down and punched a hole in them.
• A brown pupal mass with a ropey consistency.
• In late stages, dark hard scales in the cell that cannot be removed.
• A pupal tongue protruding upward in the cell.
• A foul odour in advanced infection.

The field test every learner must be able to do is the ropiness test. Take a matchstick or a toothpick. Push it into a suspect capped cell, stir, and pull it out slowly. A positive result is when the brown, snotty mass ropes out of the cell half an inch, about 13 mm, or more. It stretches like mucus. Healthy brood does not do this.

What to do about a positive result is the point where this course hands you to your national authority. Burning is the definitive answer, and the published method is to dig a sloping pit about 18 inches, roughly 45 cm, deep and wide enough to hold all the combs and equipment, about 3 feet or 90 cm, burn everything in it and bury the ash. But do not do it before you ask. In a country with an apiary inspection service, a suspect colony is a notifiable matter and destroying it may itself be an offence.

On antibiotics, understand two things. They do not eliminate spores; they suppress the visible disease and leave the contamination. Resistance is increasingly documented. In the United States the three products historically used have required a veterinary prescription since 1 January 2017. Whether any antibiotic may lawfully be used in bees in your country, by whom, under what prescription, and with what withdrawal period, is set nationally. And here is the commercial reason to care: many honey-importing markets have a zero-tolerance position on antibiotic residues in honey. One treated colony can destroy a cooperative's export contract. This course names no antibiotic.

Equipment sterilisation methods that exist include fire scorching, lye immersion, and cobalt-60 irradiation. Lye, caustic soda, is corrosive and hazardous, and should never be used without proper protective equipment and supervision. Irradiation is unavailable to most beekeepers. Scorching with a flame is the one most people can actually do, on woodwork only, not on comb.

The practical African rule that follows from the 70-year spore survival: never move comb, hive parts or honey between colonies without knowing they are healthy, and treat every second-hand hive as a permanent risk unless you know what happened to the colony in it.

European foulbrood, caused by Melissococcus plutonius, is also WOAH-listed. This course must be honest: no detailed European foulbrood source was available for it, so the usual field descriptions of how it differs from American foulbrood are not confirmed here and are not taught as fact. What is safe to teach is this: any brood abnormality that is not clearly ropey American foulbrood still needs a diagnosis, and diagnosis of foulbroods is a laboratory matter. Learn to recognise that this brood is wrong, and escalate.

Nosema, nosemosis, is not WOAH-listed but is economically significant. It is caused by two microsporidians, Nosema apis and Nosema ceranae. Transmission is oral-faecal: infected faeces are significantly sweeter, so bees ingest spores while cleaning. Signs include faecal streaking on the hive and frames, but that alone does not confirm nosema, and a swollen white midgut on dissection. The only definitive diagnosis is microscopic examination for spores. One threshold circulates, that about 1 million spores per bee requires action, and the source itself notes it lacks definitive scientific backing. Nosema reduces worker longevity, and Nosema ceranae causes precocious foraging, meaning bees forage younger than they should.

No African nosema prevalence or seasonality data was available for this course, and the seasonality reported in the literature is temperate. Treatment is a regulator matter and this course names none.

The safe teaching on nosema: it is invisible without a microscope, it is a stress disease, and the practical controls are strong colonies, clean combs, good sites and requeening. None of those requires a diagnosis.

Every control in this module reduces to four actions, and not one of them is chemical. If you take nothing else from these six lessons, take these.

1. Keep colonies strong. Small hive beetle, wax moth and to a large extent disease attack the weak. A strong colony polices its own combs, corners beetles, removes moth eggs, and rears brood fast enough to outrun a mite population.

2. Do not give a colony more comb than it can cover. Free, immediate, and it removes the habitat that both beetle and moth depend on. Use a follower board in a top-bar hive. Remove old comb the bees cannot cover during food scarcity.

3. Requeen and select from healthy, hygienic, calm stock. Kenyan bees have been reported to show Varroa-specific hygienic behaviour, and hygienic stock selection is a recommended control for beetle as well. Your record cards from Module 1 are what make this possible.

4. Never move comb or equipment between colonies of unknown status. American foulbrood spores last 70 or more years.

Now build them into a written plan. A health plan is one page and it has five parts.

Part one: your contacts. The name, office and telephone number of your national veterinary or agriculture authority, and the answer to the question of whether you are legally required to report a suspected notifiable disease. Also the national veterinary medicines or pesticide regulator, who decides which products may lawfully be applied to a hive in your country and with what withdrawal period before harvest. Get those answers before you need them, and write them on the page.

Part two: your monitoring schedule. Decide when you will do each of these and put dates in a calendar.

• A mite count on a sample of colonies. Alcohol wash or sugar shake, about 300 bees, mites counted and the percentage written down. Repeat at set points so you build a picture across the season, especially around the time adult and brood populations peak, because mite numbers peak soon after.
• A brood inspection on every colony, looking for spotty pattern, sunken greasy perforated cappings, and doing a ropiness test on anything suspect.
• A pest check on every colony: beetles running from the light, webbing, ants, frass.
• An entrance observation, which costs nothing and disturbs nothing: crawling bees with crumpled wings, dead bees outside, faecal streaking, the smell, and the weight when you heft the hive.

Remember that with African bees every inspection has a cost. Absconding is triggered by disturbance. So inspect with a checklist and a purpose, and get out. External observation is worth more here than in Europe precisely because it is free of that cost.

Part three: your standing rules for equipment. Where comb is stored, how quickly harvested comb is processed, when surplus comb is rendered into wax, and the rule that no comb crosses from one colony to another without a reason and a health check. Add the second-hand equipment rule: nothing enters the apiary unless you know what happened to the colony that was in it.

Part four: your action thresholds, written in your own words. For each pest, what you will do at what point. For Varroa, that means writing down the percentage at which you will act, and being honest in the plan that the published thresholds of roughly 1 to 3 percent are United States figures for European-derived bees whose applicability to African bees is unestablished. Record your own counts alongside your own colony outcomes for two or three seasons and you will eventually have something better than a borrowed number: your own.

Part five: your records. Every mite count, every ropiness test, every colony you lost and what you think killed it. Keep the cards from previous years. One season tells you nothing. Three seasons tells you which colonies to breed from and which pest actually costs you money on your own site.

A word on what a health plan is not. It is not a spray calendar. This module has deliberately given you no product, no dose, no concentration and no withdrawal period, and that is not a gap in the teaching. Residues in honey are a food-safety failure and an export-market failure. A honey with an antibiotic or acaricide residue is not a slightly imperfect honey; it is a rejected consignment, and in a cooperative it is everyone's rejected consignment. So the plan says: apply nothing to a hive that is not registered for bees in your own country, apply nothing with supers on, and ask before you buy.

Finally, the plan should name the two things that will genuinely kill your colonies most often, which are not on the WOAH list at all: starvation in a dearth, and absconding. Watch stores. Watch shade. Watch disturbance. A colony that is well fed, well shaded and left alone is a colony that resists everything in this module.