VIII SIMPOSIO INTERNAZIONALE ICPBR

HAZARDS OF PESTICIDES TO BEES

Bologna, 4-6 Settembre 2002

Protocolli EPPO per i test di tossicità

Registration of systemic insecticides and EPPO guidelines

Jean-Noël Tasei (1), Minh-Ha Pham-Delègue (2) and Luc Belzunces (3)

(1) Unité de recherches de zoologie, I.N.R.A. 86600 Lusignan, France. E-mail: tasei@lusignan.inra.fr
(2) L.N.C.I. I.N.R.A. 91440, Bures sur Yvette, France
(3) Laboratoire de Toxicologie Environnementale, UMR 406, I.N.R.A. Site Agroparc, 84914, Avignon cedex 9, France

French bee scientists and experts involved in the registration of agrochemicals have a special concern in the assessment of the toxicity and hazards of systemic substances to which bees are exposed. E.P.P.O. guidelines and the decision making scheme have been established only to estimate the effects of spray treatments on honey bees and they do not refer to any specific method for assessing indirect effects due to systemic insecticides and to low doses modifying adult bee behaviour or causing delayed actions.

The dispute about the possible hazards to honey bees of seed dressing treatments by Gaucho (imidacloprid) has stimulated studies aiming at the assessment of:

- the amounts of imidacloprid residues transferred to nectar and pollen,

- the delayed effects of low doses on adult mortality,

- the modifications of behaviour (learning, orientation, foraging), after a chronic exposure to sublethal doses,

- the larva susceptibility.

Some hypothesis such as the alteration of orientation capabilities could hardly be tested in cage or tunnel. In addition field testing was criticised on account of the very high D.T.50 (dissipation time 50) of the test substance and of other seed dressing insecticides, which impeded access to potential control areas deprived of soil residues. Therefore new methods had to be used by several laboratories for estimating indirect effects on adult bees of a concentration range including the concentrations determined in sunflower florets. These simple and sensitive methods were:

1) a laboratory sub-chronic test on adults,

2) a laboratory proboscis extension reflex test,

3) a test on foraging behaviour in tunnel.

In addition, the evaluation of larva susceptibility was considered because the brood can be exposed through contaminated nectar and pollen. As the method recommended by E.P.P.O. could not provide an LC50 or LD50, a larval feeding test in artificial conditions inspired from Peng et al. (1992) was used. The results should be discussed once the residues in the food transferred to the colony in realistic conditions, have been determined.

It is suggested that the development of the methods set up for studying Gaucho effects should serve for any other study case like that of Gaucho and for the registration of new systemic insecticides implying a sub-chronic exposure.

Other important concerns are:

a) possible sub-lethal effects of pesticides with a hazard ratio (dose rate per ha / LD50) lower than 50;

b) the setting up of an evaluation method for studying synergy and potentiation phenomena.