The influence of fungicides on the growth of Trichoderma asperellum

Numbers of strains of Trichoderma asperellum are known as biological control agents of certain root pathogens of tomato (Lycopersicon esculentum). The restricted use of fungicides is sometimes useful in combination with these biological control agents. Therefore some experiments were conducted to evaluate the growth of T. asperellum in the presence of fungicides as Previcur (active substance propamocarb) and Sumico (with the active substance carbendazim and diethofencarb). The influence of these fungicides was first examined in laboratory conditions. The fungus was brought on a potato dextrose agar where the fungicides Previcur, Sumico and carbendazim were added in a concentration of 0.1x, 1x and 10x the recommended dose. The growth of T. asperellum was totally inhibited by the three Sumico and carbendazim concentrations. T. asperellum knew a small but significant decrease of growth when the 10x dose of Previcur was added. Afterwards the influence of these fungicides on the fungus was tested in field conditions in the greenhouse. The fungus was applied to the roots of the tomato plant, which was grown on a rockwool medium. Previcur and Sumico were submitted to the plants using the normal procedure. The results of the tests showed that in field conditions there was no effect of the fungicide treatment on the presence of the fungus, although the laboratory tests showed the opposite for Sumico. To explain this contradiction two other experiments were conducted to follow the migration of the Sumico after treatment. A residue analysis showed that the highest concentration of Sumico was detected in the rockwool medium, and some residues were found in the drain water and the stems. Even with a 100x recommended dose of Sumico the fungus was still present the day after the treatment.