Preventing Bombus terrestris from escaping with a net covering over a tomato greenhouse in Hokkaido

Abstract

We developed a method for preventing the escape of commercial European bumblebees (Bombus terrestris) from greenhouses using plastic nets. We selected a mesh size (4.0X4.0 mm) based on the body size measurements of individual bees in five mature commercially obtained colonies. From 2004 to 2005, we covered the sides, ceiling, and entrances of more than 2,500 greenhouses with nets in Biradori-cho, Hokkaido, Japan. Compared to surveys conducted in 2002 and 2003, the number of bees collected outside the greenhouses markedly declined in 2004 and 2005, corresponding to the increasing percentage of covered greenhouses near the survey sites. Thus, covering the sides, ceiling, and entrances of greenhouses with 4.0X4.0 mm plastic mesh is an effective means of preventing the escape of B. terrestris, and reducing the density of this bee in the surrounding fields.