Every beekeeper will deal with disease or pests at some point. It is not a question of skill; it is a question of time. Varroa mites, foulbrood, Nosema, small hive beetles, and wax moths are part of managed beekeeping the same way weeds are part of gardening. The colonies that survive are the ones where the keeper spotted the problem early and acted before it spread. It covers the most common bee diseases, parasites, and hive pests, what each one looks like in a real inspection, what causes it, and what you can do about it.
What are the most common bee diseases?
Bee diseases fall into two broad groups: brood diseases that kill developing larvae and pupae, and adult bee diseases that weaken or kill the foragers and house bees. Both can wreck a colony if they go unchecked, and several show up together, which makes regular inspections the single most useful habit a beekeeper can build. Knowing how to inspect your hive and what to look for each time matters more than any treatment you can buy.
American foulbrood (AFB)
American foulbrood is the disease every beekeeper dreads. It is caused by the bacterium Paenibacillus larvae, and it is lethal, contagious, and almost impossible to eradicate once it takes hold. As few as 10 spores can infect a larva less than 24 hours old, and a single dead larva can produce over one billion new spores. Those spores survive for more than 40 years on equipment, with some sources documenting viability past 50 years. Heat, cold, and most disinfectants do not kill them.
Symptoms show up in the brood pattern. Healthy capped brood is flat and even. AFB cells are sunken, greasy-looking, and often punctured with small holes. Push a matchstick into a suspect cell and pull it out: the dead larva stretches into a brown, ropy string, sometimes two or three centimeters long. There is also a sour, sulfur-like smell that experienced keepers recognize before they pull a frame. In most states and countries, AFB is notifiable, meaning you must report it. The standard response is burning the hive, frames, and all contaminated equipment, because antibiotics only suppress the vegetative bacteria and do nothing to the spores. Prevention means keeping equipment clean, never feeding bees honey from unknown sources, and replacing the oldest frames in each box every year. Burning a colony is painful, and I have had to do it once, but the alternative is losing every hive in the yard.
European foulbrood (EFB)
European foulbrood is caused by Melissococcus plutonius, a different bacterium that also attacks larvae but is less lethal than AFB. Larvae die before they are capped, so instead of sunken caps you see twisted, discolored larvae sitting in open cells, sometimes yellow or brown. The smell is sour but less foul than AFB, and the matchstick test does not produce the same ropy pull. EFB often clears up on its own when a strong nectar flow begins, because the colony replaces dead brood faster than the bacteria can spread. Requeening with a vigorous, hygienic queen helps, and understanding how the queen shapes colony health and behavior makes the decision easier. In severe cases, antibiotics (oxytetracycline) are used in some countries, though regulations vary. Good colony nutrition and proper feeding during dearth periods reduce the stress that lets EFB take hold.
Nosema
Nosema is a gut disease of adult bees caused by microsporidian fungi, primarily Nosema ceranae. Infected bees have shortened lifespans and reduced ability to forage and rear brood. Colony symptoms are vague: slow spring buildup, dwindling population, and sometimes dysentery stains on the front of the hive, though N. ceranae often shows no visible dysentery at all. Diagnosis requires crushing a sample of bee abdomens in water and counting spores under magnification. The antifungal fumagillin has been the traditional treatment, though its availability and effectiveness against N. ceranae vary. Good apiary hygiene, strong queens, and keeping colonies well-fed go further than any drug. Maintaining a well-managed apiary that avoids overcrowding helps, since stressed colonies are the ones Nosema hits hardest.
Chalkbrood and sacbrood
Chalkbrood is a fungal disease caused by Ascosphaera apis. Dead larvae turn into hard, chalky white or grey-black mummies that rattle around on the bottom board or get dragged to the hive entrance by house bees. It looks alarming but is rarely fatal to the colony. It tends to appear in cool, damp weather and in colonies with poor ventilation. Requeening with hygienic stock and improving airflow through the hive usually clears it up. Sacbrood is a virus (sacbrood virus, SBV) that kills pupae inside their skin, leaving them looking like small fluid-filled sacs. Workers remove the dead brood, so you may notice a spotty brood pattern rather than actual sacs. Both diseases are annoying but manageable, and strong colonies with good genetics tend to clean them up on their own.
What pests attack bee hives?
Diseases come from inside the colony. Pests come from outside, but the damage can be just as bad.
Varroa mites
Varroa destructor is the single biggest threat to managed honey bees worldwide. Originally a parasite of Apis cerana, it jumped to Apis mellifera in the mid-20th century and has since spread to every continent except Australia, which confirmed its first detection in 2022. The mite feeds on the fat body of developing pupae and adult bees, weakening them directly and vectoring at least five viruses, including deformed wing virus (DWV) and acute bee paralysis virus (ABPV). Untreated colonies typically collapse within one to three years.
The numbers tell the story. US beekeepers lost 55.6% of managed colonies in the 2024 to 2025 season, the highest annual loss since national surveys began, with Varroa and its viruses as the primary driver. Backyard keepers who skip Varroa treatment see winter losses roughly 12.5 percentage points higher than those who treat. The management threshold is about 3 mites per 100 bees in late summer, measured by an alcohol wash or sugar roll.
Treatment options include synthetic miticides (amitraz strips, flumethrin), organic acids (oxalic acid, formic acid), and biotechnical methods like drone brood removal. The choice depends on the season, your local regulations, and whether your bees are producing a honey crop at the time. Keeping up with effective Varroa mite control methods is not optional if you want your colonies to survive. Monitoring is the first step, and the bees that come through winter with low mite loads are the ones that build up strongly the following spring.
Small hive beetle
The small hive beetle (Aethina tumida) is native to sub-Saharan Africa and now established in the US, Australia, and parts of southern Europe. Adults are small, dark beetles about 5 to 7 mm long that hide in crevices of the hive. The real damage comes from the larvae, which tunnel through comb, ferment honey, and leave a slimy mess that bees abandon. Strong colonies keep beetles in check by corralling them and coating them in propolis, but weak or queenless colonies can be overrun in days. Traps help reduce numbers, and keeping colonies strong is the most practical defense. Having the right pest and Varroa control products on hand before beetle season saves scrambling later.
Wax moths
Greater wax moth (Galleria mellonella) and lesser wax moth (Achroia grisella) lay eggs on unprotected comb. Their larvae chew tunnels through the wax, leaving silk webbing and dark frass that ruins frames. Wax moths rarely destroy a strong colony, because guard bees kill the moths and remove larvae. The problem comes when colonies are weak or when supers sit in storage after the harvest. Freezing frames for 48 hours kills moth eggs and larvae, and storing supers with airflow and light discourages re-infestation. Using proper honey extraction and storage equipment to get supers processed promptly keeps moths off your comb.
How do you prevent bee diseases and pests?
Prevention beats treatment every time, and most of it is basic husbandry. Keep colonies strong and well-nourished, since a large, healthy population with a good laying queen is the best defense against almost everything on this list. Requeen regularly with hygienic stock, meaning queens from lines that detect and remove diseased brood. Rotate old comb out, aiming to replace the oldest frames every two to three years so disease spores and chemical residues do not build up.
Practice good biosecurity. Do not swap frames between hives without checking for disease first. Clean your hive tool between inspections, ideally with isopropyl alcohol or a flame, and keep all your beekeeping equipment sanitized between apiaries. Do not feed bees honey from unknown sources, ever. And monitor for Varroa at least three times a year: once in spring, once after the summer honey flow, and once before winter treatment. If you are new to all of this, a step-by-step guide to getting started as a beekeeper covers the foundations, setting up your hive in the right location reduces moisture problems that encourage disease, and understanding how a bee colony actually works helps you read the signs faster.
Why does protective gear matter during disease inspections?
Inspecting a sick hive is not the time to rush. You need to move slowly, look at the brood pattern frame by frame, and hold frames at different angles to spot sunken cells or discolored larvae. That takes time, and the longer you are in the hive, the more defensive the bees get. At OZ Armour, we build our protective gear for exactly this kind of work. Our ventilated beekeeping suits keep you cool during long inspections, and we pair them with beekeeping gloves and beekeeping veils that give solid sting protection without blocking your view of the comb. For quick checks where a full suit feels like overkill, our beekeeping jackets cover the upper body, while beekeeping trousers and beekeeping ankle protection close the gaps bees find fastest. Families who inspect together can kit out younger helpers in beekeeping kids suits, and we even offer pink bee suits for keepers who want a bit of personality at the hive. A reliable smoker rounds out the kit by calming the bees long enough for you to check every frame.
When should you call for help?
If you see a brood pattern that looks wrong and you are not sure whether it is AFB, EFB, or something else, do not guess. Contact your state or regional apiary inspector. Most offer free inspections and can send samples to a laboratory for confirmation. AFB in particular spreads to neighboring apiaries through robbing and drifting bees, so a delay in diagnosis puts other beekeepers at risk. Joining a local beekeeping club or association connects you with experienced mentors who have seen these problems first-hand and can walk you through what to do. Knowing how to manage your hive through swarms, requeening, and health checks is one thing; having someone beside you the first time you open a suspect hive is another.
How do healthy hives stay healthy?
The short version: good genetics, good nutrition, low mite loads, clean equipment, and a beekeeper who pays attention. None of these are expensive or complicated on their own, but they need to happen consistently, season after season. Colonies that go into winter with young queens, low Varroa counts, and enough stores are the ones that come out strong. Understanding what it really costs to run a hive year-round helps you budget for treatments, replacement queens, and fresh frames instead of being caught out. And choosing the right bee species for your climate and region in the first place stacks the odds, since locally adapted bees with strong hygienic behavior handle disease pressure better than anything you can spray or drip on them. If you want to go deeper, learn beekeeping through our hands-on guides, or read more blogs about beekeeping for seasonal tips on every topic covered here.
Sources: Colony-loss figures from the Bee Informed Partnership national survey (2024-2025 season) and USDA research on amitraz-resistant Varroa; AFB spore longevity and infectivity data from APHIS, the Australian Department of Primary Industries, Texas A&M Apiary Inspection Service, and Penn State Extension; Nosema biology from peer-reviewed reviews including Fries (2010) and the long-term German monitoring study (Tauber et al., 2022); pasteurization and Varroa management thresholds from published COLOSS and Bee Informed data. Regulations on AFB reporting and treatment options vary by country and state; check with your local apiary authority for current rules.
