The small hive beetle (SHB), settled in Australia for with industry partners the Wheen Bee Foundation and the 15 years, has established itself as a major pest of beekeeping in regions with mild winters and wet summers, particularly in the coastal areas north of Sydney. Over the last decade, research along with industry innovations has produced a range of in-hive control options and knowledge to support better management strategies for this perennial pest. However, despite these advances there is still a need for an external trap which can be used both for monitoring the presence and movement of the SHB and the economic management of the beetle for large-scale commercial apiaries.
The RIRDC Honeybee and Pollination program, along Queensland Beekeepers’ Association have funded a three- year project to develop an external attractant trap for the small hive beetle. This project is being led by Dr Diana Leemon of the Qld Department of Agriculture and Fisheries, collaborating with Dr Andrew Hayes of the University of the Sunshine Coast. Dr Leemon recently presented at Ballina an overview of this research to the NSW Apiarists annual meeting.
Dr Leemon introduced her presentation with a brief history of the SHB in Australia, a summary of the beetle’s life cycle and outlined the damage potential of this pest to both the European honey bees (Fig 1) and native stingless bees (Fig 2).
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A summary of data collected in six surveys of registered Queensland beekeepers conducted between 2008-2016 confirmed the status of the SHB as a major apiary pest (Table 1). The greatest number of losses of hives and nucleus hives occurred in wet years. A decrease in the losses occurred over the last two surveys (2014-15; 2015-16), which presumably reflects the increase in knowledge and options available for SHB control. However during the last two seasons of the survey there was a long period of dry weather during spring which possibly slowed both SHB activity and population increase. If this is true then the potential for damage levels to increase again with a wet spring reinforces the need for further control options.
The presentation then outlined the scientific basis of the approach being taken by the research team to develop an external attractant trap for the SHB, along with the inherent challenges involved in such a project and a summary of the research to date.
All insects find their way largely by “smell”, so that each species of insect has specific odours to which it will respond. For example pheromones are odours produced by insects as a signal to other insects of the same species. These may be sex pheromones which help males and female insect find each other or they may be aggregation pheromones which tell insects to come and gather at a certain place. In addition insects also respond to non-pheromone odours such as those produced by their preferred food sources.
Research in both Australia and the US has shown that SHB are strongly attracted to a range of hive associated odours, these include adult honeybees, pollen, brood and hives products that are fermenting as a result of SHB activity (commonly known as “slime”). Dr Leemon’s research has focussed on investigating the range of odours coming from the fermented hive products/slime to find which individual chemical components of these odours are most attractive to the SHB; the aim being to make a synthetic lure based on these components. As well as developing a synthetic lure the project needed to also investigate suitable trap designs for the lure, and test the traps and lure in different apiaries to optimise trapping efficacy. As the research progressed it became apparent that this research presented a number of challenges which included making:
• An attractive and economic synthetic lure more powerful than odours emanating from a hive.
• A synthetic lure that will keep giving out the attractive odours for at least 4 – 6 weeks and a release system for the odour that will steadily release the odour over this time period.
• A suitable trapping system consisting of trap design, fast killing agent, and strategy to know when and where to deploy the traps including understanding the optimal location for taps in relation to an apiary.
• A simple method of evaluating trapping efficacy through measuring the change in SHB numbers in a hive.
To achieve these aims the research first collected honeycomb and brood from a range of geographical locations where the SHB is problematic, then used the SHB to breakdown and ferment these materials. The odours coming from these fermenting materials were sampled for chemical analysis and tested to see when SHB found them most attractive. The chemical profile of the fermented materials that were attractive to SHB along with those which were non-attractive to SHB were compared. From this a list of 14 key compounds were found to always be present in attractive fermented materials while absent in the non-attractive fermented materials. Each of the 14 key compounds was then tested to confirm attractiveness to the SHB.
Later, some of the most attractive chemical compounds were mixed together in pre-determined ratios to form a synthetic blend as a potential lure. Ten different blends have been investigated in the laboratory, with some proving to be significantly attractive to the SHB.
Parallel investigations into trap design incorporating a suitable odour release mechanism and trapping strategy needed to be conducted in order to be able to test the lures in the field. In addition a non-disruptive method to estimate SHB numbers in hives needed to be developed.
A range of traps were tested including one that had reportedly been successfully used in Florida for trapping SHB. Unfortunately no matter how strong the attractant few SHB were trapped until a simple lantern trap available through Bunnings was trialled (Fig 3). When this trap was used with a simple yeast/honey water mix, SHB were regularly trapped allowing the team to gather data on triggers for SHB movement such as temperature, moisture (humidity, rainfall), wind strength & direction and even barometric pressure (storm front) Fig.4). This design was also modified for use with a synthetic lure (Fig. 5).
The regular trapping of SHB with the yeast-based attractant was conducted at three different apiary sites: Bellbowrie and Gumdale in Brisbane and the Wheen Bee Foundation Research Apiary in Richmond. The Bellbowrie and Gumdale sites were also paired with non-apiary sites approximately 10 km away. A total of 2, 204 SHB were trapped outside of the hives at Bellbowrie between the beginning of November 2016 and May 2017. In the same time 284 SHB were trapped at Gumdale. A low number of SHB were trapped at the non-apiary sites with 19 trapped at the site paired with Bellbowrie and 3 trapped at the Gumdale paired site. In Richmond traps were deployed for a shorter period (Mid- March – early May) and 76 SHB were trapped.
By deploying the yeast-based attractant traps at different positions around the apiaries the effect of direction and distance from hives was also investigated. In Bellbowrie only 34% of SHB were trapped ≤ 20 m from the hives and 66% of SHB were trapped ≥ 90m from the hives, with many trapped as far away as 200 m from the hives. The results at Richmond supported this with 28% of SHB trapped 20 m from the hives and 72% trapped 100 m from the hives (Fig 6). Not surprisingly the prevailing winds influenced the direction of traps catching the most SHB.
Quick and non-disruptive fortnightly assessments of SHB in the hives at all three apiary sites were conducted to give a relative measure of SHB in those hives. These assessments consisted of a visual count of SHB seen when the hives were opened as well as the numbers of SHB trapped over a fortnight in trench traps and folded vinyl mats with fibrous backing (“fluffy mats”). These relative measures were validated with total hive counts of SHB. The total hive counts were conducted five times and each time the relative count measured between 37% and 40% (Average 38.6 ± 0.7 %) of the total SHB in the hive. This method can be used to assess the change in SHB numbers in hives and efficacy of an external SHB trap as shown in the graph below of SHB trapped at the Bellbowrie apiary (Fig. 7).
When the most promising synthetic lures were tested in the field, very few SHB were trapped compared to the numbers being trapped in the yeast-based attractant traps. There may be a number of reasons for this, including the need for a better odour release mechanism, a difference between SHB behaviour in the laboratory and field, or that the concentration and proportions of the synthetic lure need further adjustment. It is also likely that a synthetic lure will also be improved with the addition of a SHB aggregation pheromone. Investigations in this area have so far confirmed that SHB aggregate regardless of sex or age. Analyses of air samples collected from SHB aggregations under a number of conditions have found a range of chemical compounds. These compounds are currently under further investigation.
The external trap project was originally planned to finish in July 2017, but has been extended to the end of 2017 to allow further testing of synthetic blends and collection of field data.
The project team are grateful for the support from a range of groups contributing funds and or in-kind support to the project: RIRDC Honeybee and Pollination program; The Wheen Bee Foundation; Queensland Beekeepers Association; The Hawkesbury Beekeepers Inc., Phil and Theresa Bowman (Gumdale apiary); Various beekeepers for supplying honeycomb and brood samples.
*Dr Diana Leemon
