Pesticides Affect Honeybee Behavior

Widespread health issues of Apis mellifera, the western honey bee, have become a growing concern across America and around the globe. Drawing the most attention has been the rapid (and mysterious) disappearance of the bees from the colony, termed Colony Collapse Disorder. CCD has found its way to center stage in the debate of honey bee health and the future of honey bees as part of the global agricultural system. Pollinating over 130 agricultural plants in the United States, honeybees have an estimated value of over 15 billion dollars to agriculture to the US alone. This figure is based solely on the pollination carried out by the honey bee and not the value or benefit of bees wax and honey. With honeybee populations depleting at increasing rates, the concern is rising to the forefront as a major global concern that may leave agriculture systems dependent on foreign produce, threatening global food security. It was Albert Einstein who said that “if the bee disappeared off the surface of the globe, man would have only four years to live”. So the question then becomes, what is can be attributed to the rapid disappearance of our fuzzy friends and how can we fix it before it is too late?

Many theories have been brought to the table, such as climate change and the increased exposure to mites and pesticides, but research has led me to believe that the widespread use of agricultural chemicals are the problem. The ability of the honeybee to thrive has declined drastically in recent decades, which may be due to the generational effects as well as behavioral effects of low-level pesticide exposure. The effects of sub-lethal exposure to common agricultural pesticides are not well documented, but are hypothesized to have profound effects on foraging success, homage rates, and learning ability in Apis mellifera. The neuronal effects of many pesticides are postulated to be linked to various health disorders in the colony and may be a contributing factor to Colony Collapse Disorder (CCD). A major concern of pesticides and the subsequent effect on behavioral patterns in honeybees is derived from the neurotoxicity of these chemicals.  Exposure to low level pesticides can lead to decreases in Na+/K+ ATPase and acetylcholinesterase (AChE) activities that may directly affect learning performance as well as the possibility of affecting developmental stages, specifically the development of neural tissue of larvae.  Active foragers rely on their own memories in order to repeatedly locate food patches. Given that navigation depends entirely on nervous transmissions, any pesticide regarded as neurotoxic poses a major threat even at minute levels. Behavioral effects may range from the inability to integrate visual patterns during foraging and extend to inaccuracy of information relayed through the waggle dance performed in the hive. In addition, simple foraging techniques become impaired from body contact and/or ingestion of contaminated food sources. With impaired synaptic activity, the likelihood of successful foraging is diminished and the health of the colony is compromised. In my research, I observe the physiological effects these pesticides have on Apis mellifera and document any profound behavioral effects noted in conditioning trials carried out.

Single stimulus learning in the conditioning of Apis mellifera was carried out to determine the ability of the honeybee to access associative memory in order to navigate to and successfully forage a known food source. Apis mellifera was conditioned to an artificial food source by color that yielded the nectar of the same concentration on a consistent basis. The nectar flow occurred at approximately the same time, daily in order to maintain regularity and condition the bees to the peak artificial nectar flow provided in the trial. Individual bees were marked with numbered plates to track visitation frequency and provide information on preference as well as providing the ability to track the individuals in an observation hive. After conditioning to the recognized food source, low level pesticides were introduced into the nectar flow to determine and identify any deleterious effects on navigation and learning performance. Data is still in the process of being compiled and analyzed. In the upcoming months, trials will be carried out in the lab to determine the direct effects of low-level pesticides on honeybee flight and various innate behaviors within the colony.

-Max Kollmer



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