Sublethal effects of kaolin and the biopesticides Prestop-Mix and BotaniGard on metabolic rate, water loss and longevity in bumble bees (Bombus terrestris)

Abstract

Kaolin is an inert material with a broad range of applications, e.g. as an insecticide and as a filling substance in the formulation of biopesticides. Hence, bees that dispense biopesticides to the field in the context of entomovectoring are exposed to elevated risks because of sideeffects of those products. Here, we investigated with use of bumble bee workers of Bombus terrestris L. the lethal and sublethal effects of (i) pure kaolin, (ii) the biofungicide Prestop-Mix containing the parasitic fungus Gliocladium catenulatum and kaolin and (iii) the bioinsecticide BotaniGard containing the entomopathogenic fungus Beauveria bassiana and compared with wheat flour powder that we considered safe for bumble bees. As the most important result, treatment with kaolin increased the cuticular water loss and reduced the survival of treated bumble bees, while Prestop-Mix had no negative effect on longevity. BotaniGard caused mortality in the bumble bees because of the entomopathogenic spores it contained. In conclusion, our data indicated that substances used as 'inert materials' and in biocontrol agents which are used in IPM and organic farming systems may bring higher risks to bumble bees used in entomovector technology.

Safety of Prestop® Mix to pollinators: a critical review of its properties and use in entomovectoring. Response to the article by Karise et al. (2015)

“…In the present commentary, I argue that the exposure scenario used by Karise et al (2015) was unrealistic, and that certain other experimental methods are questionable. In the present commentary, I argue that the exposure scenario used by Karise et al (2015) was unrealistic, and that certain other experimental methods are questionable.…”

“…It is surprising that Karise et al (2015) found impacts of pure kaolin on the bees, but when mixed with Gliocladium and formulated as Prestop Ò Mix, the kaolin effect disappeared. For mixing with soil, kaolin (clay) is an ideal substance, and cannot be expected to cause any problems.…”

“…Kaolin was tested by Karise et al (2015), as it is suspected ('known') to be a major component in the formulation of Prestop Ò Mix. However, the carrier material used in BotaniGard is not 'known' and therefore, was not tested.…”

“…Alstad et al 1982;Korunic 1998;Zhukovskaya et al 2013). It should be noted also that the term 'inert ingredient' for substances that are known to have biological activity-such as the insecticidal effects of kaolin, and as used by Karise et al (2015)-is misleading. Bozic and Valentincic 1995;Macedo et al 2002).…”

“…Comparing apples and eggs Karise et al (2015) compare two biopesticides, Prestop Ò Mix and BotaniGard Ò , to evaluate the general risks for pollinators arising from the use of biopesticides in entomovectoring. But what purpose does it serve to lump in the same 'safety test' for pollinators a known insect pathogen, and a fungal antagonist proven to be harmless to insects?…”