VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Effetti di Pesticidi sui bombi e su altri apoidei

Teflubenzuron effects on the red mason bee (Osmia rufa L.): a preliminary test set up in microcosm

Paola Ferrazzi and Emanuela Elia

Di.Va.P.R.A. Entomologia e Zoologia applicate all’Ambiente "Carlo Vidano", University of Turin, Via Leonardo da Vinci 44, 10095 – Grugliasco, Torino. E-mail: paola.ferrazzi@unito.it

The effects of a commercial insecticide formulation of teflubenzuron (Nomolt®) have been tested inside a plexiglas structured microcosm set up in the Laboratory of Environmental Quality, University of Turin.

This artificial ecosystem has been articulated in two cells, each of which having a capacity of 1.5 m3. One of them was used for analysis and the other one as a control environment. Each cell had light and aeration control; temperature and humidity control was not provided to check the feasibility of avoiding this regulation in microcosms experiments.

The test species have been chosen in order to represent different trophic levels: to create a terrestrial food chain, detritus consumers have been introduced into the microcosm, in association with the primary producers Trifolium repens L. var. sylvestris and Phacelia tanacetifolia Benth. and the primary consumer Osmia rufa L., obtained from intensive rearing at the University of Pisa. An aquatic chain was also created inside each cell.

On this artificial ecosystem, teflubenzuron has been tested for chronic toxicity by spraying, on the water environment and on the flowering vegetation inside the analysis cell, an aqueous solution containing 1.5 ml of Nomolt® per litre, corresponding to the dose indicated in the instruction sheet against Leptinotarsa decemlineata (Say) on potatoes and eggplants.

Before spraying, 11 Osmia males just emerged and 10 cocoons containing Osmia females have been introduced in the biological community of each cell.

Results have been statistically analyzed. Teflubenzuron, introduced only one time at the beginning of the test, produced a rapid lethal effect on Osmia emergence from most of the cocoons and it influenced adversely different behavioural aspects of the emerged adults. This kind of damage increased during the testing period, and, after 7 days all the red mason bees contained in the analysis cell were died.

In the control cell the survivorship of the bees was 12 day; their conditions were good until the end of their lives, but this result is considerably shorter than the life period recorded for other Osmia bees in past experiments.

Probably this is due to temperature and humidity control missing; after this experience it is rather evident that this kind of regulation is essential for microcosms including not only an aquatic environment but also a terrestrial one.

Another problem to be recorded for future experiences is that, in presence of a water pond, these solitary bees tend to throw themselves in it and they often die, even if small wooden floats are placed on the water surface. The arrangement of a fine weave net on the water tub before starting microcosms experiments involving Apoidea insects is therefore recommended.