Patricia Butler, Boulder County Beekeepers' Association, April 2003
Summary: This paper was prepared to inform Colorado beekeepers about a new pest, the small hive beetle (SHB) which was first found in Colorado in 2001 and persists in that apiary despite 2 years of treatment. Based on reports from U.S. Department of Agriculture researchers and other observers, it seems unlikely that SHB will become as serious a problem in Colorado as it is in the southeast, where it has caused considerable damage to apiaries and honey crops. But because we have so little experience with SHB, it is important for Colorado beekeepers to be on the lookout for this pest (in adult and larval stages) and let others know if it is found. It can be managed with a combination of practices, such as hive location, honey house and super sanitation, and chemicals. The purpose of this paper is to provide background information about the pest and its life cycle, how to identify it, the damage it causes, possible control strategies, experience with it in Ohio and Colorado, and steps beekeepers can take to minimize its potential damage.
Introduction
Small hive beetle (Aethina tumida) was first reported in Florida in 1998 and has since spread to at least 18 states by migratory pollination activities and infected bee packages (Caron, et al. 2001). Useful information (including photographs to help identify the adult and larval stages) is available on the web, for example, from the Mid-Atlantic Apicultural Research & Extension Consortium (Penn State University) at http://maarec.cas.psu.edu1 and the US Dept of Agricultural Ag. Research Service in Weslaco TX at Weslaco.ars.usda.gov, where SHB research is under way.
Description and Life Cycle
The beetle is about 1/3 the size of a honey bee, reddish brown or black. Fully developed larvae are under ½ inch long, creamy with a brownish head. It is important to be able to distinguish them from wax moth larvae, which may be present in weak or stressed hives. Like wax moth larvae, SHB larva have 3 sets of legs near the head but do not have the pairs of 'prolegs' attached to each larval segment that are present with wax moth (and other moth and butterfly larva) (MAAREC 2000. SHB larvae have a stiffer exterior cuticle and are firmer when squashed (even hard to squash with a hive tool) than wax moth larvae, which are very soft. Finally, unlike SHB larvae, wax moth larvae make webs.
Adult females lay their egg masses near combs. Larvae are very numerous. Ellis (2002) found that a single pair of beetles produced almost 600 larvae, though only 2/3 of them become adults. They feed on pollen, wax, honey, bee eggs and bee larva for 10 - 16 days. They then leave the hive, drop into soil to pupate, and emerge as adults in 3-4 weeks. They can fly (reportedly up to 10 miles, Wenning 2001) to colonies where they deposit eggs and begin the cycle again; there can be up to 5 generations per year. They overwinter in hives or stored honey supers but do not reproduce until spring.
Damage
A minor pest in its native South Africa, SHB appears to be much more damaging to North American beekeeping, estimated to cause $3 million in damage to Florida's beekeeping industry in 1998 (Ellis 2002). Though weak hives are at greatest risk, SHB was observed to infest and kill strong hives in the southeastern U.S. (Elzen et al. 1999). South African cape bees aggressively defend their hives from this pest (Elzen, et al. 2000 and 2001) and surround them with propolis to immobilize and feed them (Ellis 2003). A recent study by Ellis (2003) revealed that European honey bees in hives where a small number of beetles were introduced "socially encapsulated" most of the beetles in propolis 'prisons,' but larger infestations can overwhelm a colony's ability to isolate the adults.2
Both adults and larvae feed on honey, pollen, bee eggs, and bee larva. Adults need pollen to reproduce. Adults alone are reported to do little damage. Rather, it is the larval stage that is most destructive, not only feeding but damaging comb and defecating into the honey, causing it to ferment (with a reportedly rotten orange odor), froth, and run out of the combs. The larvae leave a trail of slime whose odor can repel bees from the comb and may even cause the queen to cease laying and the bees to leave the hive. Adults can live 1 month in empty brood comb and over 5 months on honey, so they could overwinter in stored supers (Ellis 2002), but southeastern beekeepers have not experienced significant problems with SHB in stored comb (Cutts 2003). Honey supers awaiting extraction can become infested with larvae, which damage the comb and make the honey unfit for consumption.
Distribution
As of September 2001, the beetles had been reported in 17 states, mostly on the east and south coasts of the U.S., but also including Midwest states of Iowa, Michigan, Minnesota, and Ohio (Wenning 2001). As noted below, it also has infected at least one Colorado apiary. It has been observed that the beetles thrive where soils for pupation are sandy (Wenning 2001). They can reproduce even with the heavy, clay soils as we have in much of Colorado, but it is not known whether their Colorado infestations may be less severe.
Detection
The adults might be seen scurrying for cover when the hive is opened, or massed under the top cover or on bottom boards, hidden among debris. SHB adults are distinguishable from other beetles that may be in the hive by sharply pointed ends on the right and left of their thorax shield when viewed from above (as seen in MAAREC pictures). Because they prefer darkness and are very small, adults try to hide and may be difficult to see. They are not deterred by sticky boards (used to monitor varroa). But they reportedly will congregate in corrugated cardboard placed on the bottom board (MAAREC 2000). A plasticized corrugated material that bees will not eat might be more effective than cardboard or cardboard could be placed under the varroa screen. Larvae may be seen feeding on hive debris on solid bottom boards below screened bottom boards (therefore it is important to keep the tray below the screen cleared of debris). They are very visible when they feed on hive products and bees on the comb. Wenning (2001) reports that adults increase egg laying after supers are removed (possibly in response to stress, suggesting the importance of monitoring colonies after removing honey).
SHB can take refuge in honey supers, both waiting for extraction and in storage. While the beetle won't reproduce without a protein source, which is limited in honey supers (Ellis, 2002, Ellis et al. 2002), adults and larvae can overwinter in stored supers and re-infect hive bodies when the supers are placed on colonies the next spring. Larvae also can make a mess of stored comb.
Control
In addition to maintaining strong, healthy colonies, and locating them on heavy clay soils when possible, a combination of sanitation and chemical control is reported to reduce SHB damage. Bees appear to have some instinct to isolate adult SHB or eliminate larvae. Ellis (2003) recently reported that honey bees in Georgia (like those in South Africa) attempt to 'encapsulate' adult beetles within the hive when the infestation was low (25 or fewer SHB per colony), suggesting that European bees retain some natural instincts to isolate hive invaders.
Combs infected with larvae can be: 1) frozen at or below 10 degrees F for 24 hours (MAAREC 2000) or 2) submerged in 100% chlorine bleach solution (and not returned to the hive for 24 hours, before which time the bees will not work the comb) (Park et al 2002). Larvae found on bottom boards should be destroyed. Prompt extraction of honey supers will reduce their attractiveness to SHB. Sanitation should be maintained in the honey house; light traps near the floor attract larvae seeking a place to pupate. Although SHB is not a major problem in stored supers, stored also can be fumigated with paradichlorobenzene crystals (PDB mothballs) which controls SHB larvae as well as wax moth larvae (Caron 1997).
Researchers recommend that controls be used if any larvae are detected or there is a heavy influx of adult beetles. Two chemical controls are approved for SHB:
- GardStar. Drenching the soil (mowed clear of grass and weeds) for 18 - 24 inches in front of each hive with 1/6 gallon of a permethrin product (Y-Tex "Gardstar" ®) disrupts pupation and can provide very substantial control (Baxter et al. 2001). Avoid introducing this chemical into the hive (bee larvae can be harmed by direct contact) by applying it after dark and closing off the front entrance during application. It should be applied as soon as larvae are observed in or near the hive (not as a prevention!). It will leach out of soil with rainfall and may need reapplication every 6 - 8 weeks (MAAREC 2000).
- Coumaphos (sold as "Check-Mite+" ®) is the only chemical registered (on a temporary and emergency basis) to control SHB. It is an organophosphate, which is more harmful to humans than, for example, Apistan, and therefore requires both an EPA pesticide applicator's license3 and special use precautions such as rubber gloves. It is effective only when the beetles are active (above 70 degrees F and best applied when daytime temperatures in the hive exceed 85 degrees F and nighttime temperatures do not fall below 70). It is applied by stapling the strips to the bottom of a piece of corrugated cardboard from which one paper side has been removed and placing the cardboard in the center of the bottom board4 (below any varroa screen if one is used) with strips facing down for no fewer than 3 and no more than 45 days. Coumaphos cannot be applied more than 4 times/year. Honey supers must be removed from the hive before using coumaphos and not replaced for at least 14 days after the strips are removed. Coumaphos does concentrate in comb over time, so sale of comb honey from hives treated with coumaphos is prohibited. Coumaphos does not completely eliminate SHB but is reported to reduce adult populations to manageable numbers.
Recent SHB Experiences: Ohio and Colorado
Ohio. Three years ago, Ohio beekeepers received packages infected with SHB from South Carolina breeders, but since the infestations were small (4 - 20 adult beetles per package), they have been able to control it within two seasons using only GardStar soil drench (Flottum 2003). In an informal, uncontrolled study (involving too few colonies to produce statistically significant differences), the Ohio Dept. of Agriculture found that treatment with GardStar alone was more effective than Coumaphos alone and equally effective as Coumaphos and GardStar together. Kim Flottum advises beekeepers with such small beetle numbers to use GardStar but recommends removing supers within two days of actually seeing larvae on the comb (because supers can encourage larger populations) or many adults congregating on the inner cover or other surfaces.
Colorado. Colorado Beekeeper Ric Harris found SHB in packages he received from Georgia in 2001. He saw an adult beetle briefly run out of the package while he was storing it waiting for weather to improve. He applied both Coumaphos and GardStar during the 2001 season and found declining numbers of adult beetles on the cardboard, but populations overwintered into 2002 and again in 2003. He has noticed that SHB seem to thrive in both weak hives and hives recently disturbed (e.g., when tended), to which they can do much damage to comb. Ric is willing to speak to Colorado beekeepers about his experience (303/964-8770).
Summary
We are still learning about how serious a problem this pest may become in Colorado and how to manage it in a way that is least costly and uses the least intrusive and least toxic methods. SHB experts believe that it will never be as serious in states like Colorado with harsh winters, low humidity, and clay soils compared to southern coastal states, but local conditions might vary. Because so little is still known about this new pest, we all have a role in monitoring and reporting on experience with it, for example:
Vigilance: Colorado beekeepers (especially those who obtain packages from southern states) should be vigilant for evidence of this pest in both adult and larval stages. Information about susected infestations should be shared with adjacent beekeepers and the beekeeping community by reporting to the state or local associations.
Control: If the pest is detected early and the numbers are small, GardStar drench (which does not require a pesticide applicator's license) may eliminate it in as little as two seasons, but Ric's experience suggests it still may get out of hand. More serious infestations may require Coumaphos.
Healthy Colonies: Like all the other pest and disease assaults, SHB seems to favor weak colonies, so maintaining overall colony vitality is important.
Sanitation: Prompt extraction of supers from infested hives is critical, as is maintenance of clean honey houses and other areas where supers or empty brood comb are stored. PDB treatment of stored supers may be warranted if larvae are present.
Pollen Traps: Because SHB depend on pollen for reproduction and larval growth, it is advisable to clean pollen traps every few days.
References
Baxter, J.R., P.J. Elzen and W.T. Wilson and J.D. Kellerby. 2001 "GardStar 40% EC (Permethrin) Efficacy Trials as A Ground Drench for the Control of the Small Hive Beetle Around Honey Bee Colonies, 2000." Arthropod Management Tests 26.
Caron, Dewey M., et al. 2001 (November). "Small Hive Beetle in the Mid-Atlantic States." American Bee Journal 141(11):776-77.
Caron, Dewey M. 1997. "Other Insects," in Honey Bee Pests, Predators & Diseases, Morse, R. A. and Flottum, K, editors. Medina, OH: AI Root Publishing.
Cutts, Laurence (Florida apiary inspector). Personal communication with Pat Butler, April 15, 2003.
Ellis, James D. Jr. 2003 (February). "Incarceration of Small Hive Beetles." Bee Culture 131(2):24-26.
Ellis, J.D., P. Neumann, R. Hepburn and P.J. Elzen. 2002. "Longevity and Reproductive success of Aethina Tumida (Coleoptera: Nitidulidae) Fed Different Natural Diets." Journal of Economic Entomology 95(5): 902-907.
Ellis, James D., Jr. 2002 (July). "Food for Thought: How Diet Affects Small Hive Beetles." American Bee Journal 142(7):515-17.
Elzen, P.J., et al. 2001. "Behaviour of African and European Subspecies of Apis Mellifera Toward the Small Hive Beetle, Aethina Tumida." Journal of Apicultural Research 40(1):40-41.
Elzen, P. J., J. R. Baxter and M. Allsopp. 2000 (April). "Small Hive Beetle: Experience in South Africa." Bee Culture 128(4): 56.
Elzen, P.J. et al. 1999. "Field control and biology studies of a new pest species, Aethina tumida Murray (Coeoptera, Nitidulidae), attacking European honey bees in the Western Hemisphere." Apidologie 30: 361-366.
Flottum, Kim (editor, Bee Culture), personal communication with Pat Butler, April 2, 2003.
MAAREC Feb. 2000. Small Hive Beetle (fact sheet). MAAREC Publication 4.6 Mid-Atlantic Apicultural Research & Extension Consortium.
Park, Alexis L., Jeffrey S. Pettis, and Dewey M. Caron. 2002 (June). "Use of Household Products in the Control of Small Hive Beetle Larvae and Salvage of Treated Combs." American Bee Journal 142(6): 439-42.
Wenning, Carl J. 2001 (September). "Spread and Threat of the Small Hive Beetle." American Bee Journal 141(9): 640-43.
1 To view the photos, go to the MAAREC website, click on the "Information" button at the top of the home page, scroll down the list to "Slide Sets" and click on "view index of honey bee parasites, pests and predators;" scroll through this index and click on the SHB titles to view photos.
2 Ellis (2003) hypothesizes that this instinct developed in African bees and dwindled - but did not completely disappear -- due to lack of need after bees migrated to Europe.
3 A Private Pesticide Applicator's Certification from the EPA is required in order to purchase restricted use pesticides, such as coumaphos. This type of certification allows individuals to purchase and apply these pesticides for their own use. This certification can be obtained by first reviewing an EPA training manual (covering information on laws, pesticide types and toxicities, and personal and environmental safety) and then completing an examination about its contents. The home study materials (manual plus examination) and application form can be obtained from the EPA in Denver (800-227-8917, Ext. 7283) or some county extension offices. A web link to the EPA staff person responsible for distributing this information can be found at: www.colostate.edu/Depts/CoopExt/wildlife/cdow_permits.htm. The certification must be renewed every 4 years.
4 Recent research by Ellis (2003) regarding "social encapsulation" observed that most SHB were not imprisoned on the bottom board but rather the front and back sides of the hive body, calling into question the best location for the coumaphos strips.
