BIOLOGICAL CONTROL OF SOME CUCUMBER DISEASES UNDER ORGANIC AGRICULTURE

          Different antagonistic isolates varied in their effect against cucumber soil and air borne pathogens.
In general, Trichoderma spp. isolates were the most effective antagonists one against all tested soil borne pathogens (Sclerotium rolfsii, Fusarium solani and Rhizoctonia solani). On the other hand, Bacillus subtilis isolates and Streptomyces spp. showed slight effect against the tested pathogens.
The most effective methods in controlling cucumber damping off were soil drench or seed dressing using T. hamatum and T. harzianum. It is also clear that, Pseudomonas fluorescens and mixture of Trichoderma spp. isolates were the most effective biocontrol agents in controlling air borne diseases (powdery and downy mildew) on Premo and Fares varieties , respectively .The highest yield was obtained when only Ps. fluorescens, B. subtilis and mixture of Trichoderma spp. isolates were used . All antagonists showed the highest effect when the treatments were repeated weekly.
Cucumber plants received bioagent treatments at early stages (4 weeks old) were more healthy compare with those received the same initial treatments at 5 or 6 weeks old.