Brassica napus flower visitors in the southern Pampas, Buenos Aires, Argentina

Rapeseed, Brassica napus L., is an oil crop that, according to some authors, results in better yields with entomophilic pollination than with self-pollination alone. It is a crop of growing interest in Argentina. The objective of our study was to determine putative pollinators besides honey bees present in canola crops in the southern Pampas, province of Buenos Aires. We used trap bowls during rapeseed bloom on October 23^rd, 2013. We used a blocked split-plot design where four cultivars were located in each of three blocks. Each plot (block/cultivar) had trap bowls of six different colors (white, blue, purple, yellow, green, and red). A total of 1033 insects were trapped across all orders.  Insect orders captured were: Coleoptera 36%, Hymenoptera 35%, Diptera 14%, Homoptera 8%, Thysanoptera 6%, Lepidoptera 0.6%, and Heteroptera 0.3%.  Insect count data was square-root transformed and analyzed by insect order using ANOVA. In every order, there was no significant cultivar effect but there was a significant color effect. This trial was used as a preliminary study to determine which color trap bowls and cultivars to use in future research. Our main conclusions follow. White bowls trap more Hymenoptera than other colors and, as expected for red color-blind insects, red bowls trapped the least. White, blue and purple bowls caught more Coleoptera than the other colors. Diptera were caught in higher numbers in white and yellow bowls while red and purple bowls caught the least.  Insects caught are in the process of further identification.