CDM Diagnostic Key – Question 1 – Yes

Cucurbit Downy Mildew (CDM)

Pseudoperonospora cubensis

On cucumber, squash and pumpkin, CDM produces angular, light green to yellow lesions on the upper leaf surface.
Fig. 2. CDM on cucumber
On watermelon and cantaloupe, CDM lesions are diffuse, irregularly shaped and can be surrounded by a chlorotic halo.
Fig. 3. CDM on watermelon

Note: Initial CDM lesions can appear water-soaked and as the disease becomes more severe, lesions will become necrotic and coalesce and leaves will curl upward

Fig. 4. initial watersoaked CDM lesion
Fig. 5. severe CDM lesions and leaf curl