Precision Monitoring of Honey Bee (Hymenoptera: Apidae) Activity and Pollen Diversity during Pollination to Evaluate Colony Health

SIMPLE SUMMARY: Honey bee colonies deployed for pollination must be healthy to meet industry demand. Monitoring the activity of bees can indicate hive status but it is a complex task because bee colonies are inherently variable and require a holistic approach. In this study, we endeavored to monitor honey bee hives in the field using a combination of remote surveillance to quantify flights and by assessing the risk of pesticide exposure to bees from the pollen they collect. In Australia, vast almond orchards are grown as monoculture and in a semi-arid region, and so a lack of floral diversity may also impact bee health during pollination. Almonds are not produced without honey bees, and so it is essential to protect bee colonies, to ensure that there will be sufficient hives available in the following years. We showed that honey bee activity can be measured in the field to test for differences between hives. No insecticides were detected in pollen but combinations of fungicide residues were, although the individual concentrations were likely not hazardous. Floral diversity was perhaps less important for promoting bee activity compared to pollen availability, however, flowering weeds and trees in hedgerows may be important to help support hives. ABSTRACT: Certain crops depend upon pollination services for fruit set, and, of these, almonds are of high value for Australia. Stressors, such as diseases, parasites, pesticides, and nutrition, can contribute to honey bee Apis mellifera L. colony decline, thereby reducing bee activity and pollination efficiency. In Australia, field studies are required to monitor honey bee health and to ascertain whether factors associated with colony decline are impacting hives. We monitored honey bee colonies during and after pollination services of almond. Video surveillance technology was used to quantify bee activity, and bee-collected pollen was periodically tested for pesticide residues. Plant species diversity was also assessed using DNA metabarcoding of the pollen. Results showed that bee activity increased in almond but not in bushland. Residues detected included four fungicides, although the quantities were of low risk of oral toxicity to bees. Floral diversity was lower in the pollen collected by bees from almonds compared to bushland. However, diversity was higher at the onset and conclusion of the almond bloom, suggesting that bees foraged more widely when availability was low. Our findings suggest that commercial almond orchards may sustain healthier bee colonies compared to bushland in early spring, although the magnitude of the benefit is likely landscape-dependent.