Losses due to plant diseases may be as high as 10-20% of the total worldwide food production every year, resulting in economic losses amounting to many billions of dollars and diminished food supplies. Chemical control involves the use of chemical pesticides to eradicate or reduce the populations of pathogens or to protect the plants from infection by pathogens. For some diseases chemical control is very effective, but it is often non-specific in its effects, killing beneficial organisms as well as pathogens, and it may have undesirable health, safety, and environmental risks. Biological control involves the use of one or more biological organisms to control the pathogens or diseases. Biological control is more specialized and uses specific microorganisms that attack or interfere with the pathogens. The members of the genus Trichoderma are very promising against soil-born plant parasitic fungi. These filamentous fungi are very widespread in nature, with high population densities in soils and plant litters . They are saprophytic, quickly growing and easy to culture and they can produce large amounts of conidia with long lifetime.