Small hive beetle
The small hive beetle (SHB), Aethina tumida, is native to sub-Saharan Africa. SHB are known to detrimentally affect honey bee hives, bumble bee and stingless bee colonies, and some solitary bee nests. Apart from the European Cape honey bee subspecies, Apis mellifera capensis, that is well adapted to small hive beetle infestation, SHB has become a major pest to honey bees globally. These beetles were first detected in South Carolina and Florida in the 1990’s and has now spread to every continent except Antarctica. The widespread range expansion of small hive beetles is aided by global movement of honey bee colonies and bee products. SHB prefer climates with high humidity and temperatures, creating ideal conditions for reproduction.
Figure 1. Small hive beetle (By Audrey Sheridan, Mississippi State University Extension)
Potential establishment in Washington State
Historically, the small hive beetle has been considered a transient pest introduced from packages or bee products with little to no potential to sustain in Washington State. It has long been assumed that climate and soil conditions would exclude establishment of this species in Washington State. However, recent research has revealed that global warming may contribute to the expanse of suitable habitat for this invasive species. Under current and future climate scenarios, models of survival and pupal development times in response to soil conditions were created, then suitable areas were classified from global soil data. Beyond the theoretical modeling that has demonstrated the potential establishment of SHL in Washington; communication with multiple beekeepers seems to confirm the creation of resident beetle populations. Over the last few years, there have been reports to WSU and WSDA along with samples to verify a handful of sustained populations in different parts of Whatcom County in Northwestern WA.
I used state-of-the- art ecological niche model to make a heat map of SHB habitat suitability for Washington State, with red being the most suitable, and light blue being least suitable (Figure 1). High suitable habitat were identified in low elevation areas of Cascade Mountain in western Washington, the northeastern Washington also show climate suitable, where most areas in central Washington that are characterized by arid high desert, rolling hills and sagebrush are not climate suitable. A user-friendly website (https://gpzhu.github.io/SHB/SHB_WA.html) was also developed to facilitate public interaction with this habitat suitability prediction. If you live in these areas with greater SHB habitat suitability, beekeepers should regularly monitor and treat for SHB in areas in red, orange, or yellow.
Figure 2. Heat map of habitat suitability generated by Dr. Zhu, based on ecological niche models.