Downy mildew on pumpkin/gourd leaves
Downy mildew of cucurbits (Pseudoperonspora cubensis) can be a very destructive foliar disease as shown here on pumpkin.
Photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY
Small individual necrotic or chlorotic flecks appear on the upper leaf surface on downy mildew-infected leaves.Photo courtesy of T.A. Zitter, Cornell University, Ithaca, NY
Sporulation of downy mildew occurs on the bottom surface of leaves, giving
a purplish or brown sooty appearance.
Photos courtesy of T.A. Zitter, Cornell University, Ithaca, NY
Patches of yellow tissue on pumpkin leaves due to
Note that downy mildew spots often have an angular appearance because they do not enlarge beyond major veins. This is most evident on the lower surface.
Yellow spots are on the upper
surface of this leaf opposite where spores have developed on the lower
surface. One section of this leaf has
died because of downy mildew.