Final diagnosis


Pseudoperonospora cubensis (Downy mildew)

Several rather round, sometimes angular, light green and slightly oily to chlorotic spots form on the upper surface of a melon leaf. <b> <i> Pseudoperonospora cubensis </i> </b> (downy mildew)
On the underside of this leaf, there are recently developed wet, oily spots. <b> <i> Pseudoperonospora cubensi </i> s </b> (downy mildew)
A large patch of mildly chlorotic late blight developed on the periphery of the leaf blade. This begins to necrode. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
A purplish to blackish down, more or less inconspicuous, sometimes partially covers the spots of late blight on the underside of the blade. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
Brown to black greasy spots dot the blade of these melon leaves. Often delimited by the veins, a more or less marked chlorotic halo borders them. <b> <i> Pseudoperonospora cubensis </i> </b> (downy mildew)
When wet at first, the spots of mildew visible under the blade quickly blacken and subsequently necrotize. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
Large blackish spots, still wet and geometric in mosaic shape, dot this melon leaf. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
Large blackish lesions alter certain areas of the inter-vein tissue of this melon leaf. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
<i><b>Pseudoperonospora cubensis</b></i> on melon
<i><b>Pseudoperonospora cubensis</b></i> on melon
The many brown and necrotic spots formed on these leaves cause their deformation. <b> <i> Pseudoperonospora cubensis </i> </b> (downy mildew)
All the leaves of these melon stems were destroyed by mildew. <i> <b> Pseudoperonospora cubensis </b> </i>
All of the leaves of this melon plant are completely dried out, remaining erect and rolled up on the plant. <b> <i> Pseudoperonodpora cubensis </i> </b> (downy mildew)
This leaf, affected by numerous spots of mildew, turned yellow, necrotic and curled. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
<i><b>Pseudoperonospora cubensis</b></i> on melon
Numerous sporangiophores bearing sporangia form the grayish to mauve down visible on the underside of the blade. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
Under this leaf there are two types of sporulations not to be confused: a white one linked to the development of powdery mildew, the other dark mauve produced by <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
<i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew) on cucumber
Detail of a shrubby downy mildew sporangiophore observed under a light microscope. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)
Several more or less melanized sporangia are visible on this blade observed under a light microscope. <i> <b> Pseudoperonospora cubensis </b> </i> (downy mildew)