Abstract

The molluscicidal activity of Bacillus subtilis spore suspension and the commercial formulation of Trichoderma album (Biozeid) were tested alone and in binary mixtures against adults of Eobania vermiculata and Monacha cartusiana snails under laboratory and field conditions. The interaction patterns of the two bio-agents in the binary mixtures were wisely analyzed by calculating the co-toxicity factor to find combinations with the synergistic effect. The results revealed that the molluscicidal development of B. subtilis and Biozeid increased in the binary mixtures compared to when applied alone against both snail species in the laboratory and field. Moreover, the mortality of both species was increased by increasing the concentration of Biozeid combined with B. subtilis. The co-toxicity factor values of B. subtilis at the fixed concentration of 4 × 105 spores/ml mixed with each of 0.5 × 106 , 1 × 106 , and 1.5 × 106 spores/ml of Biozeid against E. vermiculata snails were respectively -12.03, - 9.08 and – 5.40%, which indicates an antagonism. While in the case of M. cartusiana snails, the same mixtures in the same order recorded an observed additive effect with co-toxicity factors of 11.29, 18.54, and 19.12%, respectively. It is worth noting that M. cartusiana snails were more susceptible to the tested binary mixtures than E. vermiculata snails under laboratory and field conditions. Generally, the results of the present study suggest that the combinations of the biological agents represent new effective molluscicides that can contribute to enhancing the control of land snails. Further studies are required in this regard.