Small Hive Beetle

• The small hive beetle (SHB) is an exotic pest of honey bee and bumble bee colonies and can have a significant impact on apiculture and wild bee populations.
• SHB can be found in much of the U.S., including Utah, but it is more common in the Southeast.
• SHB spreads primarily by movement of bees, bee products, and beekeeping equipment.
• Infested hives appear slimy and have an odor resembling that of rotten oranges.
• SHB infestations can be prevented by early detection, using good husbandry techniques, maintaining a high ratio of bees to comb, and keeping hives in partial to full sun.
• Chemical control options for SHB are limited due to toxicity to bees.
• Coumaphos strips placed in the bottom of hives can reduce SHB infestations.

Fig. 1. Small hive beetles (SHB) in a honey bee hive. Image courtesy of Jessica Louque, Smithers Viscient, Bugwood.org.

Adults are small, 1/4 inch (5-7 mm) long and 1/8 inch (2.5-3.5 mm) wide, flattened beetles that are oblong in shape, with clubbed antennae and shortened elytra (hard wing coverings) (Fig. 2). Females are generally larger than males. Their color ranges from reddish-brown to dark brown (almost black) and darkens with age. Note that the dusky sap beetle (Carpophilus lugubris) is a similar-looking beetle (Fig. 3) and has been found in a few honey bee hives in Utah. However, the dusky sap beetle is a scavenger, attracted to decaying fruit and vegetables, and is currently not known to impact honey bee colonies. SHB eggs are 1/16 inch (1.4 mm) long, creamy white in color, and only 2/3 the size of honey bee eggs (Fig. 4).

Mature larvae are 3/8 inch (9.5-11 mm) long and 1/16 inch (1.6 mm) wide, pearly white to beige in color, and have three pairs of legs near the head (Figs. 4-6). They have distinctive rows of body spines, and two large spines protruding from the rear. The SHB larva looks similar to the wax moth larva (Galleria melonella), but on close examination can be distinguished by their body spines and by only having three pairs of legs near the head. Wax moth larvae have additional four pairs of less developed abdominal legs, lack body spines, and can grow to double the size of SHB larvae (Fig. 6). Further, wax moth larvae produce webbing in combs and can be found scattered throughout the hive; SHB produces no webbing and often congregate in corners.

Pupae are 1/4 inch (5 mm) long and creamy white to light brown in color, but darken with age.

Life History

SHB overwinters as adults and can be found amid the honey bee cluster where it is warm. Egg-laying occurs when temperatures are between 60-112°F (Annand 2011). Females typically lay eggs in clusters of 10-30 in cracks and crevices of the hive, under sealed brood cells, or in capped honey bee worker brood. A single female can lay up to two thousand eggs in her lifetime.

Eggs hatch in 2-6 days, and then the larvae feed for 3-14 days, tunneling through comb to eat bee eggs and brood, honey, and pollen. Tens of thousands of larvae may be present within a single hive, with up to 30 larvae per cell. When larvae reach their post-feeding stage (“wandering stage”), they become attracted to light. They congregate on the bottom board and in frame corners, eventually exiting colonies typically en masse at dusk, in search of suitable pupation substrates. They are capable of migrating more than 200 yards (183 m) and can exist in this stage without feeding for up to 60 days.

Pupation usually occurs within a 20-yard (18 m) radius in the top 4 inches (10 cm) of the soil around the hive, and lasts 2-12 weeks, depending on environmental conditions. Soil moisture is essential for successful pupation; developmental time is shorter in warm (above 62-77°F) (17-25°C), moist, non-compacted soils. Following pupation, adults leave the soil and invade bee colonies individually or in swarms and are attracted by the odors emitted by host colonies. They can fly up to 10 miles (16 km) searching for new host colonies. Adults live an average of 4-6 months, but can survive up to 16 months. As many as six generations per year can occur under moderate environmental conditions.

Prevention

There is no established treatment threshold for SHB, but if large populations are allowed to build up, a bee colony can collapse in under 10 days. Therefore, the most effective control method is prevention through ensuring that bee colonies are strong and healthy so that they can better defend themselves against SHB attack. Use the following tactics to safeguard your hives:

Fig. 2. SHB adults have clubbed antennae (left), but are often observed in the hive with their head and antennae tucked under their body (right). Image courtesy of The Animal and Plant Health Agency (APHA), Crown Copyright, nationalbeeunit.com (left image); Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org (right image).

Fig. 3. Dusky sap beetle, a SHB lookalike, on an overripe melon. Image courtesy of Whitney Cranshaw, Colorado State University, Bugwood.org.

Fig. 4. SHB eggs (circled) ad larvae. Image courtesy of Jessica Louque, Smithers Viscient, Bugwood.org.

Fig. 5. SHB larvae. Image courtesy of James D. Ellis, University of Florida, Bugwood.org.

Fig. 6. SHB larvae (main image) have three pairs of legs near the head, two large spines projecting from their rear (see arrows), and body spines; wax moth larvae (inset) have abdominal legs (see arrow) and lack rear and body spines. Image courtesy of Pest and Diseases Image Library, Bugwood.org (main image); Susan Ellis, USDA APHIS PPQ, Bugwood.org (inset).

Alternatively, during sunny conditions, the top super of a hive can be placed on the hive lid for about 10 minutes. The sunlight will force the adults to the bottom of the super and onto the lid. When the super is lifted, the beetles can then be more easily observed.

Consider placing 4-mm thick corrugated plastic or cardboard strips with the corrugated side down on the bottom board near the back of the hive to further aid in detecting SHB. You may need to remove the paper from one side to expose the corrugations. The opposite and upward facing side should be covered with tape (Fig. 7) to prevent the bees from destroying and then removing the cardboard from their hive. Regularly inspect the debris under the insert for evidence of SHB.

Infested colonies may have fermented honey dripping from hive entrances, damaged and slimy combs, and dark, crusty traces that appear on the hive exterior from wandering larvae (Figs. 5,8). Heavily infested colonies typically smell like decaying oranges.

Fig. 7. Corrugated cardboard insert to detect SHB.

Fig. 8. Damage to honey bee hive. Image courtesy of Jessica Louque, Smithers Viscient, Bugwood.org.

Traps: Traps can be used to remove SHB from hives. Most traps work by drowning beetles in oil or soapy water. The traps that have been shown to be effective at controlling SHB include the commercially available Freeman Beetle Trap (Fig. 9), West Trap, Beetle Blaster, and Hood Trap, as well as the homemade Sonny-Mel Trap. See Zawislak Page 4 (2014) for detailed descriptions of traps.

Fig. 9. The Freeman Beetle Trap consists of a screened mesh bottom board and a plastic tray filled with cooking oil or soapy water and slid underneath the screened mesh. Guard bees will pursue the beetles, which then fall into the liquid and die. Image courtesy of DML. http://www.honeybees-by-the-sea.com/freeman1.htm .

Checkmite+™ strips (active ingredient: coumaphos) (Fig. 10) is the only product registered for SHB control inside the hive. Staple the strips to corrugated cardboard squares and then place the squares on the bottom board of the hive with the insecticide strip facing down. The beetles come into contact with the strips when they seek cover under the cardboard. Remove strips after 42-45 days. Honey supers should be removed before using the chemical strips to avoid honey contamination, and then replaced 2 weeks after strip removal from the hive.

Fig. 10. Checkmite+™ strips. Image courtesy of Mann Lake, www.mannlakeltd.com/checkmite-trade-10-pack.