Assessing of reproductive performance of commercial Bombus terrestris dalmatinus colonies in different conditions and some practical ways to mitigation of its invasive risk.
To better understand the potential establishment and spread of B. t. dalmatinus, we compared reproductive outputs of 45 commercially produced B. t. dalmatinus colonies, containing one queen and 50 workers in their natural habitat, greenhouse, and laboratory conditions. The total number of adult gynes and gyne pupae produced per colony was significantly higher in the laboratory colonies (100.90 ± 46.20) than in the field colonies (63.70 ± 44.70) and greenhouse colonies (28.47 ± 12.39), respectively. Although laboratory colonies significantly produced more gynes, reproductive abilities of greenhouse and field colonies show that commercial movement of bumblebee colonies for pollination could have serious impacts on natural ecosystems notably for pollination of open field crops. The nest entrance of all colonies was restricted by fitting with a queen excluder. All vents of the greenhouses were suitably covered with nets. Colonies were removed from the greenhouses about 6 weeks after initial placement. Following these measures, we prevented 266 gynes from escaping from 15 hives in 2.3 ha area of tomato greenhouse. To be 100% effective, we strongly recommend that these measures should be implemented together.