The small hive beetle, Aethina tumida, is a significant challenge for beekeepers globally. This scavenger and parasite of honey bee colonies is native to sub-Saharan Africa, where it is considered a minor pest. However, since its initial detection in the United States in 1996, it has rapidly spread across various continents, including North America, Australia, Europe, and Asia. Outside its native range, it poses a considerable threat to honey bee populations and the beekeeping industry, leading to economic losses and colony collapse.
Understanding the Small Hive Beetle
Adult small hive beetles are broad, flattened insects, measuring about 5.7 mm (1/4 inch) in length and 3.2 mm in width, with a dark brown to nearly black coloration. They have clubbed antennae and short wing covers (elytra) that do not fully cover their abdomen. Newly emerged adults are reddish-brown but darken over time.
The life cycle of the small hive beetle includes four stages: egg, larva, pupa, and adult. Female beetles can lay between 1,000 to 2,000 pearly white eggs, often in irregular masses within hive crevices or capped brood cells. These eggs are slightly smaller than honey bee eggs and hatch within one to six days, usually within three days inside a hive.
Larvae are whitish, elongated grubs with rows of small spines along their backs and three pairs of legs near their head. They grow rapidly, reaching about 1 cm (3/8 inch) in length within 14 days. Once mature, the larvae leave the hive to pupate in the soil, usually burrowing 5-20 cm deep. The pupal stage can last from two to twelve weeks, with colder temperatures extending this period. Adult beetles emerge from the soil and seek new honey bee colonies, flying several kilometers to find a host.
Impact on Bee Colonies
Aethina tumida larvae cause damage to honey bee colonies by tunneling through combs and consuming honey, pollen, and bee brood. This feeding behavior, especially on bee larvae, can weaken the colony’s population. As they feed, the larvae carry a yeast, Kodamaea ohmeri, which contaminates the honey.
This yeast causes the honey to ferment, leading to frothing and a foul odor, often described as rotten oranges. The fermented honey becomes slimy and may ooze from the comb, making it unmarketable and repellent to bees. Severe infestations can overwhelm a colony, forcing the bees to abandon the hive entirely, known as absconding. While strong colonies can sometimes manage minor beetle populations, heavy infestations can lead to the collapse of even robust hives, often within two weeks.
Recognizing an Infestation
Identifying a small hive beetle infestation involves observing visual and olfactory cues. A pungent odor resembling rotting oranges indicates fermented honey within the hive, often noticeable before opening. Upon inspection, adult beetles may be seen scurrying across combs, crown boards, or the hive floor, seeking dark, hidden areas like crevices or the underside of the bottom board when disturbed.
Look for larvae, which are less mobile than adults, found in clumps in frame corners or within comb cells. Contaminated honeycomb will appear slimy, and the honey itself may be discolored or frothing. In severe cases, trails of fermented honey may be visible dripping from hive entrances, and dark, crusty traces might appear on the hive exterior as larvae attempt to exit.
Control and Prevention Methods
Managing small hive beetle infestations involves a combination of strategies to minimize their impact. Maintaining strong, healthy colonies with productive queens is an important practice, as strong bee populations defend against beetles. Good apiary sanitation is also important; avoiding spilled honey or pollen, and promptly removing dead colonies, burr comb, or beeswax scraps, reduces attractants and breeding grounds for the beetles.
Physical control methods include in-hive traps with mineral or vegetable oil to drown beetles, or corrugated plastic strips on the bottom board to trap them. Placing hives in sunny, well-ventilated locations helps, as beetle eggs are susceptible to desiccation. Some beekeepers also apply beneficial nematodes, such as Heterorhabditis indica, to the soil beneath and around hives. These microscopic worms prey on pupating beetles, disrupting their life cycle. Chemical treatments are available, but their use requires careful adherence to regulations to prevent contamination of honey products.