Abstract
Honey bees (Apis mellifera L.) are important pollinators and yet, an increasing number of reports suggest honey bee populations worldwide are in decline. Pollinators face many environmental stressors, including exposure to pesticides. Chlorpyrifos is an organophosphate pesticide that is used extensively in New Zealand. This thesis examines whether exposing bees to chlorpyrifos, applied to a forage crop at a concentration recommended by the manufacturer, alters honey bee foraging activity, or colony temperature.
A 1.26ha crop of Phacelia tanacetifolia was planted in the Ida Valley of Central Otago, New Zealand, and sprayed with 0.20kg a.i/ha of Lorsban 50EC. The spray event occurred in early January 2017, the height of the austral summer. Honey bee colonies were introduced to the crop either, prior to the spray event or at intervals thereafter. Colonies exposed to pesticide were compared with colonies located on control (untreated) sites.
HiveMind monitors, a satellite based measurement system, were used to provide a real time count of foraging activity and a record of internal hive temperatures in all colonies. Activity and temperature measurements were taken every three hours over a 4 month period.
Significant changes in maximum activity levels and in-hive temperature were identified in all colonies. The results suggest these changes were mainly driven by shifts in forage availability and external temperature over time. There was no clear evidence linking chlorpyrifos exposure to either the decline in activity levels, or to changes in colony temperature. However this may be due to the length of the experiment which may have required a longer study period to observe pesticide effects, or the effects were masked due to other environmental factors. Further work is required to ascertain whether in the longer term, chlorpyrifos alters colony productivity.