small hive beetle infestation

A. tumida is considered to have secondary pest status in its native area of southern Africa, where it is a scavenger of weakened bee colonies. However, in areas where it has been introduced the reports are very different, and it causes significant damage to colonies (Delaplane, 1998), although weak colonies, along with those with a surplus of combs stored in them, are more attractive to bees. It is these factors that will encourage their rapid growth (Calderón et al., 2006).

As well as honey bees, bumble bee (Bombus terrestris) colonies can also be parasitized under experimental conditions; commercial B. impatiens colonies in North America have also been found to be infested (FERA, 2010). Although infestation has not been observed in wild Bombus spp. populations they should be considered susceptible (OIE, 2012).

A. tumida is native to sub-Saharan Africa; it has been introduced to the USA, Canada, Mexico, Jamaica, Australia and Italy, and reported but not substantiated in Egypt (Thomas, 1998; OIE, 2013; FERA, 2010; Delaplane, 1998; Cuthbertson et al., 2013b; Mutinelli et al., 2014). The Distribution table contains records for all countries where it has been introduced, but in the native range only for those countries where records are readily available.

In sub-Saharan Africa, where A. tumida is native, it acts as a scavenger of weakened colonies. The beetles damage weak or stressed colonies, abandoned honeybee nests and stored bee products of the African subspecies of honey bees (Kokkinis, 2005). Much more severe signs of infestation have been observed in areas where the parasite has been introduced. For example, in Florida, considerable damage and colony loss has been reported and beetle larvae tunnel though combs, kill bee brood and ruin combs. Bees have been reported to abandon combs and entire colonies that have become infested in Florida (Delaplane, 1998).

Fermenting honey, causing a frothy mess in supers and honey houses, is a sign that beetles have been defecating in the honey. In Florida, it was reported that the fermenting honey smelt like rotting oranges (Delaplane, 1998).

Schafer et al. (2008) investigated a method for diagnosing A. tumida in field colonies of bees using corrugated plastic strips, designed to house the beetles while preventing access to bees. They reported an overall strip efficacy of 35.4±20.6 % and that numbers of A. tumida in the traps correlated with total numbers in the hives.

Bottom boards, such as those reported by Torto et al. (2010) in Kenya, can be used to monitor the occurrence and seasonal abundance of the beetle in honey bee colonies. Baited Langstroth hive bottom board trap captures indicated that the beetles were present throughout the year in small numbers, but were most abundant in the rainy season.

Ward et al. (2007) reported a DNA method for screening hive debris for A. tumida. The method uses real-time PCR alongside automated DNA extraction and was able to detect DNA from eggs, larvae and adult beetles from Africa, Australia and North America. The method was found to be reliable because extraction efficiency was consistent between hive debris samples.

Stedman (2006) provides further information on how to detect and identify A. tumida and distinguish them from similar-looking insects.

Prevention

OIE (2012) makes recommendations for minimizing the risk of introducing A. tumida with bees or apiculture equipment or products. These include inspection of consignments, transporting live bees only from areas known to be free of A. tumida, covering bee consignments with fine mesh to keep beetles out, cleaning of equipment and freezing of honey.

Control

As A. tumida is not restricted to beehives but can survive and reproduce in other natural environments, feeding on other resources such as fruit, it is very difficult to eradicate from an area (OIE, 2012).

Cultural control

Simple measures to help prevent infestation by A. tumida include good husbandry practices, such as ensuring the area of the honey house is clean and reducing the amount of time that filled supers are left standing and cappings are exposed. Beekeepers should be aware that supering colonies, making splits, exchanging combs, or the use of Porter bee escapes can aid the spread of beetles or provide more room for beetles to become established away from the cluster of protective bees (Delaplane, 1998).

Host resistance

Bee hygienic behaviour refers to cell uncapping and the removal of diseased or parasitized larvae, as well as other nest-cleaning and defensive traits; African bees keep the beetle population at low levels in this way (FERA, 2010). Bee resistance to brood infectious diseases can be increased by selecting for hygienic bees. In a factsheet about the small hive beetle, Delaplane (1998) suggests that colonies should be monitored for hygienic behaviour and queen lines found to be beetle-resistant should be propagated. Even though bees will not normally clean supers, or equipment that is contaminated with beetle-fermented honey, they may finish the job if a beekeeper washes out as much honey as possible first.

Chemical control

A. tumida larvae migrate to the soil surrounding colonies in order to pupate, so a soil insecticide is recommended for their control (Delaplane, 1998); Annand (2008) suggests using permethrin. Colonies themselves can be treated with coumaphos-impregnated beehive pest control strips. Neumann and Hoffman (2008) investigated the efficacy of bottom boards and coumaphos strips for the control and diagnosis of small hive beetles in Australia. As with other studies (e.g. Buchholz et al., 2009), they reported that coumaphos traps were efficient, but mortality assessment showed that only a limited proportion of beetles were affected at the colony level. It was concluded that bottom boards provide a first estimate of infestation levels.

Coumaphos is actually an acaracide, but has been shown to be effective against A. tumida. Ellis and Delaplane (2007) investigated the efficacy of acaracides in 3 chemical classes, including organophosphates (coumaphos), pyrethroids (fluvalinate) and botanical extracts (thymol, camphor, menthol and eucalyptol). The acaricides varied in their toxicity to A. tumida, but it was concluded that there was potential to develop chemical controls based on these data.

Schafer et al. (2009) investigated the effects of organic acid treatments on A. tumida and the associated yeast, Kodamaea ohmeri. Organic acids are used to control other bee pests and were applied using the standard concentrations. Lactic, formic and acetic acids were shown to inhibit the growth of K. ohmeri under laboratory conditions. Acetic acid was found to be effective against the adult beetles and formic acid significantly reduced larval infestation.

Stored equipment can be fumigated with aluminium phosphide (phosphine); care is needed as this is very toxic (Annand, 2008).

Pesticide treatment carries a risk of residues in honey (OIE, undated).

Biological control

Other control measures that have been suggested as part of integrated control management programmes include entomopathogenic nematodes (e.g. Cabanillas and Elzen, 2006; Muerrle et al., 2006; Ellis et al., 2010; Cuthbertson et al., 2012). Ellis et al. (2010) evaluated the potential of 7 nematode species. The results of generational persistence and field bioassays suggested that Steinernema riobrave and Heterorhabditis indica displayed potential to control the beetles at tolerable levels as part of IPM schemes in bee colonies.

Other

Other investigations have looked at the use of lime, diatomaceous earth, or organic acids as alternative control measures for small hive beetles. Buchholz et al. (2009) investigated the use of slaked lime, powdered limestone and diatomaceous earth; they concluded that the best-performing formulation of diatomaceous earth showed potential as an in-hive treatment and suggested that further research was required for slaked lime.

World: IBRA, International Bee Research Association, Unit 6, Centre Court, Main Avenue, Treforest, RCT, CF37 5YR, UK, www.ibra.org.uk

World: OIE (World Organisation for Animal Health), 12, rue de Prony, 75017 Paris, France, http://www.oie.int/

UK: British Beekeepers’ Association, National Beekeeping Centre, Stoneleigh Park, Stoneleigh, Warwickshire, CV8 2LG, UK, www.britishbeekeepers.com

23/03/2012: Original text by:

Dr Claire Beverley, CABI, Nosworthy Way, Wallingford. OX10 8DE.