Biocontrol agents may employ several modes of action therefore, it is important to know the proportion and timing of each mode of action that may occur.for root diseases Fusarium oxysporumagainstFusarium oxysporum Trichoderma harzianumagainst root diseases Gliocadium virensfor seedling diseases Trichoderma harzianum/polysporumagainst wood decay. Trichoderma virideagainst timber pathogens Trichodermaspp. The following biocontrol agents have already been registered: Agrobacterium radiobacteragainst crown gall Bacillus subtilisfor growth enhancement Pseudomonas fluorescensagainst bacterial blotch Pseudomonas fluorescensfor seedling diseases Peniophora giganteaagainstFommes annosus Pythium oligandrumagainstPhythiumspp. Good soil biocontrol systems have been reported for species ofFusarium, Sclerotium, Sclerotinia, Phythium ,andRhizoctonia.The successful control by biological means in the phyllophane that have been reported in the literature involve mainly rusts, powdery mildews, and diseases caused by the following genera of pathogens:Alternaria, Epicoccum, Sclerotinia, Septoria, Drechslera, Venturia, Plasmopara, Erwinia,andPseudomonas.We can now think of microorganisms with inhibitory activity against plant pathogens as potential sources of genes for diseases resistance. Plants and microorganisms can now be manipulated to deliver the same mechanism of biological control, as has been done for the production of the delta endotoxin-encoding gene transferred fromBacillus thuringiensisto plants to control insect pests.The growing interest in biocontrol with microorganisms is also a response to the new tools of biotechnology.To meet these criteria, superior strains, together with delivery systems that enhance biocontrol activity, must be developed.Potential agents for biocontrol activity are rhizosphere-competent fungi and bacteria which, in addition to their antagonistic activity, are capable of inducing growth responses by either controlling minor pathogens or by producing growth-stimulating factors.īefore biocontrol can become an important component of plant disease management, it must be effective, reliable, consistent, and economical.However, there is an equally great or greater need for biological control of pathogens that presently go uncontrolled or only partially controlled.Nevertheless, a moderately effective, but consistent agent, seems to be sufficient to establish nonchemical control of plant disease or to reduce the level of chemical residues in agricultural products.The performance of a biocontrol agent cannot be expected to equal that of an excellent fungicide although some biocontrol agents have been reported to be as effective as fungicide control. Commercialized systems for the biological control of plant diseases are few.Biological control is a potent means of reducing the damage caused by plant pathogens.This follows an over 40-year period, starting in the mid 1920s, when biological control of plant diseases moved from the discovery of suppression in response to organic materials added to the soil.Studies aimed at replacing pesticides with environmentally safer methods are currently being conducted at many research centers.Environment Protection Agency (EPA) indicates that, in the United State alone, 30006000 cancer cases are induced annually by pesticide residues on foods, and another 50100 by exposure to pesticides during application. It is reported that over 70 pesticides have been detected in groundwater in 38 states in the United States.Plant disease control, therefore, has now become heavily dependent on fungicides to combat the wide variety of fungal diseases that threaten agricultural crops.These practices include use of genetically similar crop plants in continuous monoculture, use of plant cultivars susceptible to pathogens, and use of nitrogenous fertilizers at concentrations that enhance disease susceptibility.Biocontrol of Bacteria and Phytopathogenic Fungiĭespite the many achievements of modern agriculture, certain cultural practices have actually enhanced the destructive potential of diseases.