The bee community and its relationship to canola productivity in homogenous agricultural areas

Abstract

Canola crop productivity is benefited by bee pollination and it has been shown that bee communities can be affected by landscape composition. The aim of this study was to analyse the bee community and its relationship to canola seed production in agricultural areas. The density, abundance and richness of floral visitors of Brassica napus cultivar Hyola 61 in six commercial fields in southern Brazil were studied, and their relationships with seed production and the ratio of semi-natural, forested and agricultural areas surrounding the crops were examined. It was observed that canola fields of southern Brazil are surrounded by a homogeneous landscape dominated by agricultural areas. The survey of bees detected a low abundance and richness of native bees in contrast to the high abundance of Apis mellifera. Except for a negative correlation between the abundance of honey bees and the proportion of forested areas within a 2000 m radius from the field (R = -0.90; P = 0.012), no other correlations were found among bee abundance and richness and landscape composition. Although there was not a relationship between A. mellifera and seed set, there was a positive correlation between insect density and seed weight per plant (R = 0.87; P = 0.024). As honey bees were the most captured insect (79%), much of the pollination in this system was probably achieved by honey bees.