Trichoderma-based biological control agents are compatible with the pollinator Bombus terrestris: A laboratory study

The potential value of biofungicides for the control of important plant pathogens, such as the gray mold Botrytis cinerea, requires investigation due to the general requirement for very low pesticide residues in foodstuffs, and concerns over the increasing development of resistance to the different classes of chemical fungicides. Furthermore, the use of bumblebees as pollinators in agriculture and horticulture has become more widespread in recent years, which has generated the need to determine the potential risks of biological control agents against these insects. This study investigated the side-effects of two commercial Trichoderma-based biofungicides against the bumblebee Bombus terrestris. The two commercial compounds tested were Binab-TF-WP and Binab-TF-WP-Konc, both of which contain combinations of Trichoderma harzianum ATCC20476 and Trichoderma polysporum ATCC20475. The bumblebees were exposed to the biocontrol agents under laboratory conditions at their respective maximum concentration in the field (MFRC), and then exposed via three potential routes of exposure: dermal contact, orally via the drinking of treated sugar water, and via treated pollen. The treatments were evaluated through recording worker mortality (lethal effects) and any effects on the production of drones (sublethal effects). The laboratory tests demonstrated that the two Binab products did not cause worker mortality or adversely affect reproduction. In addition, we investigated whether the Trichoderma-based products could survive or grow on the bodies of the adult workers. In no case was survival or growth of the biofungicide observed on the workers. When the effects of these compounds were evaluated against bumblebee larvae (third and fourth instars), no entomopathogenic effects were found. Overall, the results obtained under laboratory conditions indicate that the two Binab products are safe for use in combination with B. terrestris.