Pests and diseases in honey bees

Native to Asia, varroa mites (V. destructor and V. jacobsoni) are external parasites of brood and adult bees that deform bees, reduce bee lifespans, transmit viruses, and cause parasitic mite syndrome. Infested colonies will die without intervention. Mites are small (1.1 mm long by 1.5 mm wide), oval-shaped, flat, and red-brown. 

Varroa destructor is now established in NSW and expected to spread to neighbouring states. WA seeks to use quarantine measures, geographic isolation and regular surveillance to maintain freedom from this pest. 

Varroa jacobsoni is generally limited to Asian honey bees. There have a number of examples of recent host shifting. Varroa jacobsoni has been identified and eradicated from Queensland multiple times. 

Varroa are very difficult to see during general hive inspections. These tiny mites are approximately the size of a sesame seed and often lodge in the crevices of a bee’s exoskeleton or under their abdomen. If you see varroa mites on your bees, the hive is likely heavily infested, giving the mite plenty of opportunity to spread to neighbouring bee colonies. 

With varroa mite expected to spread across Australia’s east coast in the next few years, it is critical that WA beekeepers regularly check and report their findings. Reporting surveillance results, even if mites are not detected, is important as it provides evidence and confidence that specific pest remains absent from WA. 

As the mite is difficult to see, beekeepers must use a test to accurately undertake surveillance or determine a mite load for varroa. There are several nationally recommended methodologies. Taking your time to understand each methodology and applying it consistently and frequently will provide confidence.  

Native to Asia, Tropilaelaps mites (T. clareae and T. mercedesae) are external brood parasites that transmit viruses and cause parasitic mite syndrome and colony decline. Mites are oval, 1 mm long by 0.5 mm wide. Adult mites are fast-running, often seen moving rapidly across the brood combs. Juvenile (larvae/nymph) mites are white and found in the brood cells. 

European foulbrood (Melissococcus plutonius) is a moderate brood disease that can be eradicated with management; established in eastern states of Australia. Larvae die, turn yellow-brown and become contorted in a ‘C’ position, eventually drying to a loose scale. Sometimes ropes like AFB, but mostly with a lumpy or granular appearance. Odour of diseased larvae is foul and sour. 

Red dwarf honey bees (Apis florea) (RDHB) arrived on the Burrup Peninsula, WA, in March 2023. An emergency response is ongoing. RDHB have not been found outside of the restricted Quarantine Area. Any sightings of suspicious bees should be reported immediately to the Exotic Plant Pest Hotline 1800 084 881. 

RDHB are native to Asia and have invaded the Middle East and Africa. Bees are small, 7-10 mm long, with red-brown abdomens and even black and white stripes. Nests are a small (usually less than 25 cm wide) single comb built in open air, i.e. wrapped around a branch. 

The Asian honey bee (Apis cerana) is native to Asia and is present in Queensland. Bees appear similar to EHB, but are smaller (10 mm long), less hairy, with a uniformly striped abdomen. Nests have multiple combs (like EHB), but are smaller, often in, smaller man-made cavities (i.e. letter boxes). 

The Giant honey bee (Apis dorsata) is native to Asia. A. dorsata are similar colour to EHB, but considerably larger (17-20 mm long). Nests are a large (up to 1.5 m wide by 1 m long) single-comb, built in open air, i.e. hanging from a branch or cliff. Rison considered to be the most defensive honey bee. 

American foulbrood (Paenibacillus larvae) is a major brood disease that is fatal to colonies and expensive for beekeepers. Dead brood turn into a brown semi-solid with a foul odour. Initially, dead brood have a glue-like consistency producing a long, smooth rope when probed (pictured), but eventually dry to a hard scale. Capped cells are sunken, dark-coloured, greasy and/or perforated.

Chalkbrood (Ascosphaera apis) is a moderate brood disease that reduces hive population and productivity. Fungus affects sealed and unsealed brood. Dead brood can be covered with a fluffy downy mould before drying out to a shrunken, brittle, and chalky mummified-larvae. Mummies are usually white, but can be grey-black (covered in spores), and are loose in comb. 

Nosema (Nosema apis) is a moderate microsporidian disease that affects honey bee digestive systems, reducing worker lifespan and weakening the colony. Most apparent when nutrition is poor and weather is cold and wet, i.e. autumn to early spring. Common symptom is dysentery: brown, diarrhoea on frames (pictured) and the outside of the hive.