VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Effetti di Pesticidi sui bombi e su altri apoidei

Toxicity of three pesticides on larval instars of Osmia cornuta (Latreille) (Hymenoptera, Megachilidae)

Donato Tesoriero, Bettina Maccagnani, Fabrizio Santi, Giorgio Celli

Dipartimento di Scienze e Tecnologie Agroambientali, University of Bologna, via Filippo Re 6, 40126 Bologna, Italy. E-mail: bmaccagnani@entom.agrsci.unibo.it

Osmia cornuta has been found as a good pear pollinator. In the perspective of establishing wild bees population in pear fields, three substances with fungicide action (kresoxim-methyl - Stroby®, copper oxychloride) and insecticide action (Quassia amara extract), considered safe an non-toxic for adult bees, were preliminarly investigated regarding their impact on the preimaginal development of O.cornuta.

The biological material for the experiment was obtained by O.cornuta females nesting in a cabbage seed production net tunnel. Four groups of 30 individuals (both eggs and larval instars) with their maternal provisions were put in gelatine capsules. Three of them were respectively added with 1 µl of the field dose of one of the three pesticides, the fourth acting as natural control. The field doses were respectively: Stroby® 14 g/hl; copper oxychloride 100 g/hl; Quassia amara extract 400 cc/hl; a fifth group of eggs and larvae taken from their own provision and transferred on another one served to evaluate the manipulation damage.

The toxic impact of the three pesticides has been evaluated considering the mortality in the different larval instars during development. Stroby® resulted the most safe for O. cornuta larval instars being the final mortality not different from control (respectively 13.3% and 10.0%); Quassia amara extract had the most toxic effect (mortality 82.8%), followed by copper oxychloride (44.8%). No manipulation damage was evidenced, being the mortality of the manipulated control group identical to the natural control (10.0%).