Résumé
A preliminary bibliographic study concerning the acaricide effect of sulfur reveals methodological problems and contradictory results. In order to assess the conditions wich can modulate its toxic action, the acaricide effect of sulfur (micronised wettable sulfur) was studied on three developmental stages (eggs, protonymphs, females) of Tetranychus urticae Koch. Three parameters were tested: the temperature, the humidity and the dose of application. Whatever the conditions tested, the mortality was complete for protonymphs and high for adults.[br/]The female fecundity and the viability of the progeny decreased when temperature and/or humidity increased. The toxic effect of sulfur on eggs (which was never proved before) depended on the combined influence of temperature and humidity, from a threshold temperature of 27°C and a threshold humidity of 75%. This study allows us to confirm that sulfur is toxic to T. urticae. The extension of this work will allow us to know in what proportion sulfur could be involved in controlling phytophagous mites.