Several pots and field experiments were conducted during 1997 (fall season, 1998 and 1999 (summer seasons) to study the possibility of using some safety combinations (prepared in Mansoura Research Laboratory), some microelements and biological agents in controlling downy mildew, improving growth and yield of cucumber plants, Results of pot experiments could be summarized as follows; the best treatments of the highest suppresive effect on downy mildew disease (lowest disease severity %) were TS-3 (0.02 and 0.04%), S1 (5 and 10 ml/L), MnSO₄ (0.5 an d1 gm/L) those which recorded the lowest disease severity % between 1.0 and 5.4%, whereas control plants were strongly infected (their disease severity was 95.3 and 96.7% at the two seasons, respectively. Also, plant guard (bio-agent) (2, 4 ml/L) had  an considerable suppresive effect. For field experiment, the selected best treatments from pots experiment were used herein. The best treatments of the lowest disease severity and the highest growth and yield parameters were: TS-3 (0.02%), which reduced the severity of disease by 82.8%, increased dry weight by 143.7% and fruit yield by 166.6% relative to the control. These values were 77.6, 111.0 and 158.3%, respectively for S1 (5 ml/L); 70.8, 93.0 and 125.0% for MnSO₄ (0.5 gm/L); 40.8, 85.1 and  116.0%, respectively for plant guard (4 ml/L). The results also indicated that some safety agents (nutritive micro- and macro-elements) alone or in combinations as (MnSO₄, KOH and H₂SO₄) could be efficiently used in safety and economic concentrations in controlling the pathogenic fungus (down mildew) paralleled with improving growth and yield of plants. Meanwhile, the results of statistical correlation between disease severity % and some characters confirming the present findings.