Great New Paper Out: Effects of Pesticides on Bees

Continuing with the pollination theme, here’s a new paper out on the topic:

Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae


Recent declines in honey bee populations and increasing demand for insect-pollinated crops raise concerns about pollinator shortages. Pesticide exposure and pathogens may interact to have strong negative effects on managed honey bee colonies. Such findings are of great concern given the large numbers and high levels of pesticides found in honey bee colonies. Thus it is crucial to determine how field-relevant combinations and loads of pesticides affect bee health. We collected pollen from bee hives in seven major crops to determine 1) what types of pesticides bees are exposed to when rented for pollination of various crops and 2) how field-relevant pesticide blends affect bees’ susceptibility to the gut parasite Nosema ceranae. Our samples represent pollen collected by foragers for use by the colony, and do not necessarily indicate foragers’ roles as pollinators. In blueberry, cranberry, cucumber, pumpkin and watermelon bees collected pollen almost exclusively from weeds and wildflowers during our sampling. Thus more attention must be paid to how honey bees are exposed to pesticides outside of the field in which they are placed. We detected 35 different pesticides in the sampled pollen, and found high fungicide loads. The insecticides esfenvalerate and phosmet were at a concentration higher than their median lethal dose in at least one pollen sample. While fungicides are typically seen as fairly safe for honey bees, we found an increased probability of Nosema infection in bees that consumed pollen with a higher fungicide load. Our results highlight a need for research on sub-lethal effects of fungicides and other chemicals that bees placed in an agricultural setting are exposed to.

Pettis, J.S., E.L. Lichtenberg, M. Andree, et al. July 2013.  PLOS ONE, 8:7 Article Number: e70182   DOI: 10.1371/journal.pone.0070182

Exploring the relationship between cranberry and its honey bee pollinators

In agriculture, the efficiency of pollinators is often talked about from the perspective of influence on plant yield.  Less often is the benefit of the plant to the pollinator considered.  This article does just that, and comes up with some interesting findings on how Vaccinium cropping systems affect the health of pollinator (specifically, honey bee) communities.

Pollen diversity collected by honey bees in the vicinity of Vaccinium spp. crops and its importance for colony development


Access to a rich diversity of flowering plants is very important for the development of honey bee colonies introduced in crops for pollination. The aim of this observational study was to determine the impact of surrounding pollen diversity on the health of honey bee colonies introduced in lowbush blueberries (Vaccinium angustifolium Ait.) in June and cranberries (Vaccinium macrocarpon Ait.) in July. The results suggest that monocultures of lowbush blueberries are not suitable for optimal brood rearing. In the blueberry environments we studied, the dominant pollen collected by honey bees were Alnus Mill. spp. and Taraxacum officinale F.H. Wigg., which are deficient in some essential amino acids. Significant reduction of brood rearing during honey bees’ stay in blueberry monocultures in June may, therefore, be explained by nutritional deficiencies. In July, the polliniferous flora in the vicinity of cranberry monocultures was poorer but of better nutritional quality. Pollen analysis allowed the identification of Brassicaceae, Trifolium L. spp., and V. macrocarpon as the three dominant taxa collected by honey bees during this period. The complete lists of plant taxa foraged by honey bees for pollen during the pollination of lowbush blueberries and cranberries are provided.

If you would like to read the article in full, here is the citation information and a link to where you can access it for free:

Girard, M., M. Chagnon, and V. Fournier. July 2012. Pollen diversity collected by honey bees in the vicinity of Vaccinium spp. crops and its importance for colony development. Botany 90 (7): 545–555.

Cranberry Pollination Research at the University of Wisconsin

In the spring and summer of 2012, Hannah Gaines, a PhD student in the Entomology Department at the University of Wisconsin, did experiments in the field and in the greenhouse to better understand what non-bee factors may be influencing cranberry pollination.

Hannah's cages

Monitoring one of my pollination treatment cages in the field.

Hannah's greenhouse experiment

Hand pollinating cranberry plants in the greenhouse.

Hannah's greenhouse experiment

Hand pollinating cranberry plants in the greenhouse.

To learn more about her work on native pollinators, see this article.