Downy mildew disease of cucumbers, caused by Pseudoperenos cubensis is very destructive disease which affect both plant growth and yield production. In this investigation, some safe trials were tested in order to control this disease. The maine obtained results could be summarized as following:


Bilqis cucumber cultivar showed the least susceptibility to downy mildew disease (Pseudoperenos cubensis) while Baracoda cv. was the highly susceptible one.
Bilqis cultivar produced the best average of fruits yield during the growing season and Baracoda cv. produced the least fruit yield per plant.
Application of NPK fertilizers to the soil significantly decreased the disease incidence compared to control.
Increasing nitrogen fertilizer dose showed significant increment of the disease incidence.
Increasing potassium fertilizer doses to showed significant reduction of the disease incidence.
Phosphorus fertilizer gave little effect in reducing the disease severity.
Cucumber fruit yield was highly increased in response to the increasing of both nitrogen and potassium fertilizers dosage.
Spraying the tested plant using water extract (Aloe vera 2,4and 6 ml/l, Basil 2,4 and 6 ml/l and Mint 2,4 and 6 ml/l ) on cucumber plants reduced the disease severity and increased yield production, significantly in comparison with control. Aloe vera extract showed the best efficiency and mint extract was the least effective.
Application of the plant essential oil (Castor 2.5,3.5 and 4.5 ml/l , Thyme 2.5,3.5 and 4.5 ml/l and Mint 2.5 ,3.5 and 4.5 ml/l ) to cucumber plants significantly decreased  downy mildew incidence disease and increased yield production, compared to control. Castor oil showed the best efficiency followed by Thyme essential oil. Increasing the concentration of any tested oil gave more efficiency in cucumber fruit yield, and vice was versa.

10. Single application spray of Trichoderma harzianum was more effective in reducing downy mildew disease, compared to those of T. viride and/or Bacillus subtilis. Integration of T. harziemum and B. subtilis showed the best efficiency in reducing the disease and increasing yield production.
11. All tested fungicides significantly (Folio Gold 2,2.5 and 3 ml/l , Galben 1.5 ,2 and 2.5 g/l , Amistar Top 1.5 , 2 and 2.5 ml/l and Dithane M45 1.5, 2 and 2.5 g/l ) reduced the disease incidence than control, Folio Gold fungicide was the best tested one in reducing the disease incidence. However, the best yield production was obtained when Galben fungicide was applied. Dithane M-45 fangicide was the least effective one, on both disease incidence and/or yield production.