Effects of biological control agents on the beneficial pollinator, Bombus terrestris

Bumblebees, which are already used in modern greenhouses for their pollination capacity, may provide a useful tool to disseminate biological control agents (BCAs) to the target crops to control plant pathogens. This study investigated the effects of crop-protecting biological products on the economical important pollinator, Bombus terrestris. Four commercial Trichoderma products (Binab T-vector, Binab TF WP, Binab TF WP Konc (Binab products contain T. harzianum ATCC 20476 and T. polysporum ATCC 20475) and Trianum (Trichoderma harzianum T-22)) and three biological insectides: Botanigard (Beauveria bassiana GHA), Naturalis (Beauveria bassiana ATCC 74040) and Preferal (Paecilomyces fumosoroseus) were tested. These different BCAs were applied via three different routes of exposure under laboratory conditions: dermal contact and orally via the drinking of sugar water and via pollen. In the first series of experiments the bumblebees were exposed to the maximum field recommended concentration (MFRC). These tests showed that the Binab products, Naturalis and Preferal didn't cause acute worker toxicity nor caused an adverse effect on the reproduction (production of drones). However, significant higher worker mortality was seen after dermal contact and after the drinking of sugar water with the MFRC of Trianum (up to 47%) and with the MFRC of Botanigard (up to 90%). This severe toxicity caused a dramatic reduction on the reproduction. Overall, the results indicate that the Binab products, Naturalis and Preferal at their MFRC are safe to be used in the vectoring system. Furthermore the biofungicide Trianum can be used but with caution. Finally, the bio-insecticide Botanigard is probably not compatible with B. terrestris as the worker mortality was still 50% at the ten fold dilution of the MFRC.