Invasive Bees Impact Australia's Fauna and Flora?

Honey bees were introduced to Australia in 1882 for the honey and exotic crop industry which is worth around $90million annually as of 2018. These bees where uncontrolled, allowing feral populations to spread and grow, however their exact reach and abundance is still unknown. What I can tell you is that they are a large source of competition for our native pollinators, a few bird species for nesting sites and in extreme cases they are competition for limited water sources. These bees also pollinate not only native flora, but exotic weedy species as well, which promotes the spread of the exotics.

One of the bigger concerns regarding the large feral bee populations is that they are compatible with these parasitic mites, and letting them increase their feral populations is just creating pools for this mite to infest if the parasite makes it to Australia. If the mite where to successfully invade, then extermination of feral honey bees must be done to save the large Australian honey industry from devastating losses.

So let’s see why these bees are so successful and what we need to begin to consider to make a model that will assist in managing these feral bee populations.

Ecological impacts

Encouraging exotic weeds

There is already a competition between pollinators, however feral honey bees have an advantage over native Australian bees. Honey bees have been observed pollinating native flora however their advantage is being able to recognise and access non-native flora. This is Lantana camara, or commonly known as wild sage, a major toxic environmental weed.

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This exotic weed is just one of many non-native flora that feral bees recognise as potential pollen. A correlation has been observed between the rapid spread of exotic species and the presence of non-native honey bees. With higher competition, native flora and their native pollinators are under threat of the spread of both non-native flora and honey bees.

Nesting site aggression

Another way the honey bee is potentially impacting Australian fauna is it’s competition for nesting sites with native birds such as the regent parrot, which is vulnerable to extinction. Like the feral bee, these parrots nest in hollowed trees such as red gum close to a water and pollen source. These two species overlap in preferred nesting sites but longer studies must be done to determine a definite correlation between the two species. If feral bees are taking nesting sites then they would be responsible for the smaller population size of the native fauna they were inhibiting.

Spatial dynamics

When managing these bees, the environment must be considered before any management can be deployed. High density of feral bees are shown to occur in urban areas and undisturbed sites such as wet subtropical forests and woodlands. This is because there is a large number of nesting sites, floral resources and low pesticide compared to agriculturally managed sites or large open spaces with minimal floral activity (Hinson, E, 2015).

The time of year that sampling is taken does affect how dense feral bee populations will be. It has been found that bee density decreases in Summer, due to the heat and limited water resources. New swarms do not have a set month they appear, as the success of virgin queens mating depends on weather and temperature, however some studies suggest September to October in some areas is the optimal swarming season. To let you all just get a glimpse of the abundance and increasing rate of population sizes we are dealing with I will take an example from a study done in Wyperfeld National Park in North-West Victoria.

They found that established colonies could survive for 6.6 years and new swarms could survive for 2.7 years. However, for a population to stay stable, the colony must produce 0.75 new swarms per year. Which means that at minimum, a stable population will produce 6 new swarms in its lifetime which then produces 2 new swarms each over the 6 years they where created. In only 1 established population, over 6.6 years it would create a minimum of 18 new hives which can then independently become a new established population, this study estimated there was 50 to 150 established bee populations in their area of study alone. This is just an small example at how rapidly these populations can increase over a relatively short period of time. If the resources are available, which they usually are in undisturbed forested areas, non-pesticide farms and the year round nutrients of urban living, then colonies are free to increase in size and density.

So, if we wanted to manage the feral bee population, you must consider more than the one population of bees as there are plenty to re-establish in an area that you potentially exterminate. Therefore, annual extermination must be pursued if the goal is to keep population size in that one general area down.

Management

As shown by the spatial dynamics, it would be next to impossible to eradicate this species completely due to its wide spread and abundance. However, managing smaller populations within urban areas or conservation parks is feasible and has been done before. 3 methods are used at once. To physically find a population, beelining can be used. Once a bee finds a food source it will go directly back to its hive and recruit other bees. This creates a straight line of bees from a food source to the hive. Once the hive is found, pesticides can be directly deployed. This however is a long a tedious method with only minor results alone. The second method is pheromone lures, which uses the same chemicals that a virgin queen uses to attract drones, along with the use of pesticides to kill the captured drones. This method however is only effective in high density sites. 

Then the last method used is to supply acephate, an insecticide mixed with the bait solution for the workers to carry off to their hives. But this only works if enough insecticide (around 30mg) reaches a single hive instead of being spread between many. Additionally, management of exotic weed species in the area that the honey bee normally forages from could also be considered as the bee relies on these sources for food along with native flora. This 3 method strategy however is expensive, estimated to cost more than $5524 per km2 per year. To maximise effectiveness of this process, this purging should be done when bee populations are swarming (towards the end of the year) and in areas of high bee hive density or potentially high density.