*5.1.1 Downy mildew of Cucumber*

Downy mildew is one of the important foliar diseases of members of *Cucurbitaceae* family. Unlike other cucurbits, cucumber is more susceptible to downy mildew [73]. *Pseudoperonospora* spp. is the causative pathogen of downy mildew on cucurbits generally [74]. The disease was reported on *C. sativus* L. in Egypt [75].

Serious losses result from downy mildew of cucumber under unfavourable environmental conditions. Temperature and humidity have been identified as important factors for disease infection and development [76]. The transmission of the fungus is dependent on the presence of infected cucurbit hosts in cultivated fields. Symptoms of downy mildew in cucurbits are almost exclusively confined to the leaves. In cucumber, characteristic symptoms are angular chlorotic lesion on foliage. The underside of leaf turns grey-brownish to purplish black with high humidity.

### *5.1.1.1 Management of Downy mildew*

Planting should be planned to coincide with the time that environmental factors are less favourable to disease infestation. Crop should also be closely monitored for early identification of incidence of the disease. Adoption of good phytosanitary measures, use of healthy planting materials, chemical fungicides and bio-control agents are other effective means of managing the disease.
