Most Common Bee Diseases and How to Treat Them: A Beekeeper's Guide
The most common bee diseases are: Varroa mite (most destructive — treat with oxalic acid or approved miticides), American foulbrood (bacterial — no treatment, infected hives must be destroyed), Nosema (gut fungus — improve ventilation and nutrition), chalkbrood (fungal — re-queen and improve ventilation), and small hive beetle (pest — use beetle traps and maintain a strong colony). Test for Varroa at least 4 times per year.
In This Article
1. Varroa Mites — The #1 Threat to Bee Colonies
Varroa destructor is the single most destructive honeybee pest worldwide. Untreated colonies typically collapse within 1–3 years. Every beekeeper must monitor and treat for Varroa — no exceptions.
Varroa Mite (Varroa destructor)
Critical — Treat ImmediatelySigns of Infestation
- Visible reddish-brown mites on adult bees
- Bees with deformed, crumpled wings
- Crawling bees near entrance unable to fly
- Spotty, sunken brood pattern
- Alcohol wash count above 2% (2 mites per 100 bees)
How to Test
- Alcohol wash: 300 bees in alcohol, count mites
- Sugar roll: same count method, bees survive
- Sticky board: count mite drop over 24–48 hours
- Test threshold: treat above 2 mites per 100 bees
Oxalic acid (Api-Bioxal) — most widely used, effective, and bee-safe. Apply by vaporisation or drizzle when colony is broodless. Formic acid (Mite Away Quick Strips) — effective on mites in capped brood. Amitraz strips (Apivar) — slow-release strips, highly effective. Always remove honey supers before treating. Test 4+ times per year.
2. American Foulbrood (AFB)
American foulbrood is the most serious bacterial disease of honeybee brood. It is highly contagious, has no approved treatment, and is a notifiable disease in most US states.
American Foulbrood (Paenibacillus larvae)
Critical — Report to AuthoritiesSigns
- Sunken, discoloured (dark brown) brood cappings
- Foul smell — described as rotting flesh
- Ropiness test: brown stringy thread when twig is pulled from infected cell
- Spotty, irregular brood pattern
What NOT to Do
- Do not move frames between hives
- Do not share equipment
- Do not attempt to treat — there is no approved treatment
- Do not sell or give away equipment from infected hive
AFB is a notifiable disease — contact your state apiarist immediately. Infected colonies and equipment must be destroyed by burning in most jurisdictions. Spores survive in equipment for decades. Prevention: never feed bees honey from unknown sources, inspect regularly, and buy bees only from reputable suppliers.
Regular inspections — every 7–10 days during the active season — allow you to catch disease early when intervention is most effective.
3. European Foulbrood (EFB)
European foulbrood is less severe than AFB but still a serious threat that can weaken or kill colonies, especially in spring when colonies are stressed.
European Foulbrood (Melissococcus plutonius)
Serious — Act PromptlySigns
- Dead or dying larvae — twisted, melted appearance
- Yellow-brown discolouration of larvae
- Sour smell (less severe than AFB)
- Spotty brood pattern
- Larvae die before cells are capped (unlike AFB)
Triggers
- Nutritional stress — poor forage
- Rapid population growth outpacing food supply
- Cold, wet spring conditions
- Weakened colony immunity
Oxytetracycline (Terramycin) is approved in the US for EFB prevention and treatment — follow label instructions carefully. Re-queening with a hygienic queen strain is highly effective. Improving nutrition through supplemental feeding supports colony recovery. Mild cases often resolve naturally as the nectar flow improves.
4. Nosema
Nosema is a fungal gut disease that disrupts bee digestion and reduces colony strength, particularly in late winter and early spring when bees have been confined for extended periods.
Nosema (Nosema apis / Nosema ceranae)
Serious — Monitor and ManageSigns
- Brown streaking (dysentery) on hive exterior
- Weak spring buildup after winter
- Reduced colony lifespan
- Bees unable to fly, crawling near entrance
- Confirmed by microscopic spore count
Prevention
- Good hive ventilation year-round
- Adequate winter food stores
- Early spring cleansing flights (warm days)
- Avoid damp hive locations
- Feed protein supplements in late winter
Fumagillin is approved in some countries but has limited US availability. Focus on prevention: ensure adequate ventilation, feed high-quality stores, and position hives to receive morning sun. Re-queening with hygienic queens reduces susceptibility. Most colonies recover naturally with improved spring conditions.
5. Chalkbrood
Chalkbrood is a fungal disease that mummifies bee larvae into hard, chalk-like pellets. It is rarely fatal to a colony but weakens it significantly if left unmanaged.
Chalkbrood (Ascosphaera apis)
Moderate — ManageableSigns
- White or grey mummified larvae in cells
- Chalk-like pellets visible at hive entrance
- Spotty brood pattern
- Most common in damp, cool conditions
Management
- Improve hive ventilation
- Move hive to drier, sunnier location
- Re-queen with hygienic queen strain
- Remove mummified larvae from hive floor
- No approved chemical treatment exists
There is no approved chemical treatment for chalkbrood. Re-queening with a hygienic queen is the most effective intervention — hygienic queens produce colonies that detect and remove infected larvae before disease spreads. Improving ventilation and hive positioning resolves most cases naturally within one season.
6. Small Hive Beetle
Small hive beetles (Aethina tumida) are a destructive pest primarily in warm southern US states, though they are spreading northward. A strong colony can usually control small numbers, but a weak colony can be overwhelmed quickly.
Small Hive Beetle (Aethina tumida)
Moderate — Regional ConcernSigns
- Small dark beetles (5–7mm) visible in hive
- Slimy, fermented honey in combs
- Larvae tunnelling through comb
- Bees abandoning infested sections
Management
- Maintain strong, populous colonies
- Use beetle traps (oil traps in corners)
- Keep hive in full sun — beetles prefer shade
- Remove excess empty comb
- CheckMite+ strips (Coumaphos) — approved treatment
The best defence against small hive beetles is a strong, well-populated colony. Bees police beetles effectively when the colony is not stressed. Avoid leaving empty supers or frames in the hive — these provide unguarded space for beetles to breed.
7. Wax Moth
Wax moths destroy comb and stored equipment but are primarily a problem for weak colonies and improperly stored frames — a healthy, strong colony manages wax moths on its own.
Wax Moth (Galleria mellonella)
Moderate — Equipment RiskSigns in Hive
- Silken tunnels through comb
- Larvae and cocoons visible on frames
- Comb destroyed and webbed together
- Primarily seen in weak or dead colonies
Stored Equipment
- Freeze frames for 48 hours before storage
- Store in sealed bags or containers
- Stack boxes with ventilation gaps
- Para-moth (paradichlorobenzene) for stored supers
Keep colonies strong — a populated colony prevents wax moth naturally. For stored frames: freeze for 48 hours to kill all life stages, then store in sealed containers. Never store frames with honey or pollen long-term — this attracts moths and other pests.
Varroa Monitoring Schedule
Test for Varroa at minimum 4 times per year using the alcohol wash method (most accurate):
- Early spring — before adding supers, to establish baseline mite load
- Mid-summer — mite populations peak in July–August in most regions
- Late summer / early autumn — critical pre-winter treatment window
- After autumn treatment — to verify treatment was effective
Treat when alcohol wash shows 2 or more mites per 100 bees (2%) during the active season, or 1% in autumn before winter cluster forms. Do not wait for visible symptoms — by the time deformed wing virus is visible, the colony is already severely compromised.
About SkogHive: SkogHive is a Sweden-based beekeeping equipment brand offering Flow Hive compatible hive systems, protective gear, and accessories for beekeepers worldwide. Learn more at skoghive.com →
Keep Your Colony Healthy with Quality Equipment
A well-maintained hive is a healthy hive. Browse SkogHive's range of beehive equipment, protective gear, and accessories — shipped worldwide.
Shop SkogHive Equipment →Frequently Asked Questions
What is the most common bee disease?
Varroa mite infestation is the most common and most destructive bee health problem worldwide. Untreated colonies typically collapse within 1–3 years. Regular monitoring and treatment with approved miticides is essential for all beekeepers.
How do I know if my bees have Varroa mites?
Signs include visible reddish-brown mites on adult bees, deformed wing virus (crumpled wings), crawling bees near the entrance, and spotty brood pattern. Confirm with an alcohol wash test — above 2 mites per 100 bees requires immediate treatment.
What is American foulbrood and how do I treat it?
American foulbrood is a highly contagious bacterial disease that destroys bee brood. Signs include sunken dark brood cappings, a foul rotting smell, and the ropiness test (brown stringy thread when a twig is pulled from an infected cell). There is no approved treatment — infected hives must be destroyed by burning. It is a notifiable disease in most US states.
What is Nosema and how is it treated?
Nosema is a fungal gut disease that causes dysentery, weak spring buildup, and reduced colony lifespan. Prevention focuses on good ventilation, adequate nutrition, and early spring cleansing flights. Most colonies recover naturally with improved spring conditions and good management.
How do I treat chalkbrood in my hive?
There is no approved chemical treatment for chalkbrood. Re-queen with a hygienic queen strain and improve hive ventilation. Most colonies recover naturally once conditions improve. Remove mummified larvae from the hive floor during inspections.
How often should I test for Varroa mites?
Test at least 4 times per year: early spring, mid-summer, late summer/early autumn (critical pre-winter window), and after autumn treatment to verify effectiveness. Use the alcohol wash method for the most accurate count.
0 comentarios