The development of plant defence stimulants to increase host resistance represents anattractive alternative to fungicides for the protection of crops against plant pathogens. In this study we evaluated the efficiency of 14 products presumed to induce plant defence mechanisms against Botrytis cinerea on tomato and lettuce. Two days after the application of the products, tomato and lettuce leaves were inoculated with B. cinerea and incubated in conditions conducive to disease development.Out of 14 products tested, Serenade Max® (Bacillus subtilis QST713) proved to have a significantprotective efficacy against B. cinerea on both plants. To assess the presence of low susceptibility to Serenade Max in populations of B. cinerea, the protective efficacy of this product was evaluated against 20 strains differing in their geographic origin, host of isolation and level of aggressiveness. To this end, tomato and lettuce leaves were treated with Serenade Max two days before inoculation. The efficiency of the product was significantly influenced by the isolate of B. cinerea tested with protection levels ranging from 40% to 86% on tomato leaves and 0 to 80% on lettuce leaves. No correlation was observed between the level of aggressiveness of B. cinerea strains and the protection provided by the biocontrol agent.