This study was conducted in order to evaluate the effectiveness of some plant extracts, namely Eucalyptus camaldulensis leaf extract and Cinnamomumzy lanicum extract (cinnamon). At concentrations of (0.5, 1.0 and 1.5) % (w/v) and the filtrate of the bio-control fungus Trichoderma harzianum at concentrations of (50, 75 and 100) % (w/v) in controlling the cucumber dropping off disease caused by the fungus Pythium aphanidermatum under laboratory and greenhouse conditions. The results showed the effectiveness of the bio-control fungus T. harzianum filtrate in inhibiting the growth of the fungus p. aphanidermatum in vitro" by increasing the concentrations used where the 100% concentration treatment achieved the highest rate of inhibition of the growth of pathogenic fungi, where the percentage of inhibition was 98.75%, and the concentration treatment 1.5% achieved the highest rate of 89.21 and 58.39% for the extracts of eucalyptus leaves and the study plant in inhibiting the growth of the fungus p. aphanidermatumrespectively.The results of the study, under greenhouse conditions, showed the excelled of the treatment of the bio-control fungus T. harzianum infiltrate in reducing the infection rate of the pathogenic fungus P. aphanidermatum and the percentage of healthy plants growing in soil contaminated with pathogenic fungus and treated with fungus filtrate after 7 and 30 days exelled on the treatment of soil contaminated with pathogenic fungus and treatment with plant extracts (eucalyptus leaves and cinnamon plant extract) The following rates were achieved (77.97 and 74.57% for the fungus filtrate treatments, 66.33 and 63.53% for the eucalyptus leaf extract and 53.70 and 52.27% for the cultivar extract for the periods 7 and 30 days, respectively. These results indicate the possibility of using some plant extracts and control elements Bio control to chemical pesticides in the management of cucumber seedling dampping fall disease pathogens.