Dear  Al-Janabi 

Plant resistant varieties when available. Cucumber varieties with moderate to high level of resistance are available, moderate to low levels of resistance is available for melons. Some resistance available in pumpkins and winter squash but this tends to be specific for certain pathotypes of Downy Mildew and may not be effective in all cases. Use drip irrigation and wide row spacing to promote leaf drying and encourage good air movement around the plants. Monitor plants for symptoms of disease especially from August through harvest. If the disease is found in a home garden, plants should be immediately removed and destroyed to prevent the spread to other plants. Fungicides are effective if applied before disease becomes severe. Both contact and systemic fungicides are registered for use against downy mildew. Systemics are more effective if weather conditions are conducive to disease and the host is very susceptible. Turn lights on during night. Illuminating either leaf surface of plants growing under protected conditions during nighttime was shown to effectively suppress downy mildew. However using the same systemic fungicide repeatedly can result in fungicide resistance. It is important to rotate systemic fungicides or tank mix with a contact to avoid this.

Thank you and Good luck

Dear Prof. Dr. Jawad, 

I agree with Assist. Prof. Ahmed.

You also can see the attached articles :

Best greeting

Dear Prof. Dr. Jawad,

You can also depend on the following attached articles .

With my best regards

Dear Prof. Dr. Jawad, Good morning .

You can also read the following items .

Good luck

What about oospores? If you do a baiting test to control oospores, you might be able to get the best biocontrol agents. I think, the problem actually arises from oospores which are in the soil 

Tnanks to all of you Drs (Ahmed Al mayahi, Yehya A. Salih and Aqleem Abbas) for useful suggestions and informations

Please see:

http://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/Cucurbits.aspx

http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/plant_pathology_and_ecology/powdery_and_downy_mildews_on_greenhouse_crops.pdf

http://www.agriculturejournals.cz/publicFiles/171020.pdf

https://www.ncbi.nlm.nih.gov/pubmed/21534461

http://www.vegetablegrafting.org/wp/wp-content/uploads/2013/12/1-s2.0-S0261219412001871-main-keinath.pdf

Dear Dr. Gonzalo Galileo Rivas Platero

Thanks alot for sending a valuable references for both powdery and downy meldew in cucurbits

sir,i have paper on chemical control but not on biolgical control but you can read this,if can help....

Article EFFECTIVENESS OF NEW FUNGICIDES AGAINST CUCUMBER DOWNY MILDE...

Jawad Abood Al-Janabi,

I agree with our colleague who suggested resistant varieties being the first resort. In addition to varieties in greenhouses we can address the humidity and temperature to advantage. Water such be applied without wetting the leaf surface greatly reducing disease environments. Spacing of the plants may also be important. Biocontrols which could be effective at least partially are Bacillus subtilis bacteria and Trichoderma fungi. Moreover some botanical products also can be efficacious including Cloves Cinnamon and potentials some oils such as neem. In terms of biorational nontoxic fungicides Phosphonates would be something that could be employed without a lot of issues related to more toxic based fungicides. These generally act by stimulating a host resistance action rather then direct toxicity. Some of these techniques can be combined or rotated to control problematic issues. 

Thanks to mohammad Idrees for useful references and to Paul Reed Hepperly for very valuable suggestions to control downy mildew in cucurbits