Methods of netting greenhouses to prevent the escape of bumblebees

Abstract

We assessed several methods for deploying nets over windows and entrances so as to prevent the escape of the adult European bumblebee, Bombus terrestris, from greenhouses. Bumblebees were completely prevented from escaping from glass-based greenhouses by both netting windows and filling gaps around windows with sponge, tape and/or building tamping materials. For windows in greenhouses constructed from plastic-covered steel pipe frames, bumblebees did not escape when nets were set under the plastic film and over steel frames and fixed to the outside of the steel frames, but they did escape when nets were set under the steel frames and fixed to their inside. When an entrance was netted, double netting was imperfect even with a room in front of the entrance; however, a net with a zipper completely prevented bumblebee escape. Bumblebees escaped through ventilation fans irrespective of whether they were operating, and thus netting was required, but they did not escape through fresh-air inlets. Our results indicate that it is possible to completely prevent the escape of bumblebees by netting windows and entrances, but close attention is required.