Honey Bee Pollination Enhances Bean Crop Productivity

Rizzardo, R. A. G., Milfont, M. O., Da Silva, E. M. S., & Freitas, B. M.  2012.  Apis mellifera pollination improves agronomic productivity of anemophilous castor bean (Ricinus communis).  Anais da Academia Brasileira de Ciências 84(4):  1137-1145.

http://www.ncbi.nlm.nih.gov/pubmed/22990600

                In their 2012 study, Rizzardo et al. observed pollination pathways of castor beans and recorded various degrees of productivity outcomes.  Castor beans are a major agricultural product harvested for their high oil content for the synthesis of biodiesel.  The primary method of pollination for castor beans, Ricinus communis, is self-pollination, but it can also be supplemented by wind pollination to neighboring plants and biotic pollination with insect species; primarily the honey bee, Apis mellifera.  Rizzardo et al. 2012 focused their study on the effects of A. mellifera pollination.  These methods include a primary function:  direct pollen transfer from male stamens to female pistils on alternate plants, and a secondary function:  the indirect pollen aggravation upon honey bee visits allowing stamens to more adequately release pollen for self-pollination or wind pollination.  The study team hypothesized that beans pollinated with biotic pollinators would be more productive compared to beans pollinated without the presence of honey bees.  The Rizzardo et al. 2012 study was conducted in Piaui, Brazil, but, although these were South American plants, the castor bean is also a major agricultural product of North America.  Therefore, the results of the study are applicable to agricultural methods intercontinentally.

In Piaui, Brazil, Rizzardo et al. 2012 observed a 3150 hectare castor bean plantation during the months May to June 2006.  Eighteen plots were organized into equal rectangular areas and lettered alternately A through V without the letters N, Q, and R.  The plots were surrounded with unplanted lands, and the entire plantation was encompassed by dense primary forest.  Each plot was subdivided into halves with the treatments of introduction or absence of honey bee populations.  The plots were subsequently observed for productivity of bean count and pollination effectiveness.  The investigators took daily recordings of flower counts (male and female) of each plant, presence of honey bees and other biotic pollinators, and behavioral actions of individual honey bees around the plants.  Plants were also individually treated and measured for production.  Individual plant treatments included methods of ‘bagging’ the plants, hand pollination, biotic pollination, and wind pollination (control).

After their study, Rizzardo et al. 2012 were able to make specific conclusions based on their results.  The primary method of pollination throughout plot areas was self-pollination via gravity or wind facilitation.  The second most common method was biotic pollination by honey bees or other insect species.  The least used method by castor beans for pollination was deemed to be wind pollination amongst neighboring plants.  Although it was not the primary mode, the most productive plants were those that were pollinated by honey bees.  Based on these results, honey bees near crop fields may be an adequate and natural method of augmenting production of agricultural products such as castor beans.  Concessions need to be made to accommodate honey bees.  The use of commercial products such as fertilizers, herbicides, and insecticides would be highly detrimental to honey bee populations.  The installation of honey bee colonies alongside farms could be a safe alternative to decrease the amount of harmful products introduced into ecosystems encompassing commercial farms.