VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Acute contact toxicity on honey bees – 2 answers for 2 questions

Stephan Schmitzer, Birgitta Wewer and Silvio Scazzari

Institut für Biologische Analytik und Consulting IBACON GmbH, Arheilger Weg 17, 64380 Rossdorf, Germany.
E-mail: stephan.schmitzer@ibacon.com

To assess the acute contact toxicity of pesticides to Honey Bees, OECD Guideline 213 or EPPO 170 Guideline for the evaluating of side effects of plant protection products are taken into account. The recommendation of the guideline is to apply test items to the dorsal side of the thorax of the bees at a volume of 1 µL.

One of the aims of our experiments was to investigate, whether there is a difference in sensitivity of dorsal as compared to ventral application to the honey bees. The other experiments should give us an answer to the question whether there are differences in the impact of chemicals and the applied droplet size.

Two independent sets of experiments were conducted in summer 2001. One set of experiments with a dorsal and ventral application of 4 doses of Dimethoate in parallel. The second set of experiments with applications of 3 different droplet sizes (1, 2 and 5 µL). Each experiment was conducted twice. Perfekthion EC (400 g/L Dimethoate) was used as the reference substance (containing 1 % wetting agent) at 4 dose rates (0.30, 0.20, 0.15 and 0.10 µg a.i. per bee). During application the bees were anaesthetised with CO2. Control bees were anaesthetised and treated with water/wetting agent only. During the test the bees were exposed in incubators at 25 °C and 48 – 60 % rel humidity. Mortality was assessed after 2 hrs, 24 and 48 hrs following the applications.

According to the present results, applying a droplet to the ventral side of the bee thorax seems to have a stronger effect to the bees than to the dorsal side. On the other hand the droplet size does not influence the extent of the effect of chemicals.