Miniature dispenser-based bioassay to evaluate the compatibility of powder formulations used in an entomovectoring approach

BACKGROUND: Entomovectoring as a plant protection strategy demands the design of an appropriate bioassay to assess the
risks of potential side effects of the powder formulations in the dispenser towards the vectoring insect. This study reports
on the development of a laboratory miniature-dispenser-based bioassay. This bioassay system was used to investigate the
compatibility of five model products, Prestop-Mix, Signum, kaolin, wheat flour and cellulose, with the bumblebee, Bombus
terrestris L.
RESULTS: The laboratory one-way miniature-dispenser bioassay showed that the fungicides and the carrier/diluent kaolin
caused a worker mortality of >70% after 5 weeks of exposure, while worker loss with wheat flour and cellulose was no higher
than in the blank control (i.e. empty miniature dispenser) (comprised separated passageways and demonstrated that only kaolin was toxic (89 ± 11%). These results were also confirmed
in a flight-cage experiment. In addition, a negative effect was observed against reproduction/colony development when nests
were exposed to kaolin (P <0.05) in the two-way miniature-dispenser and flight-cage bioassays.
CONCLUSIONS:In the context of entomovectoring technology, thedeveloped laboratory two-wayminiature-dispenserbioassay
gives a reliable prediction of thehazards associated withpowderproducts.Additionally, thepresent data indicate thepossibility
of using cellulose and kaolin as respective negative and positive control carriers/diluents in future risk assessment experiments.
Overall, the results show that, apart from kaolin, the tested fungicides and carriers/diluents are safe to be usedwith B. terrestris.
c 2012 Society of Chemical Industry