The underside of a cantaloupe leaf showing downy mildew lesions. Often, spore masses are not visible to the naked eye, but are nonetheless present. They can be seen with a 20X hand lens. Downy mildew on cucumber. Sporangia detach from their sporangiophores very easily.
Downy mildew can cause a variety of symptoms.
On this pumpkin leaf, massive infection occurred after heavy rains. Anthracnose on cucumber caused by the fungus Colletotrichum orbiculare . Note the tan spots characteristic of early infection. Note how the center of the lesions is cracking and dropping out. It is not uncommon to see this disease virtually wipe out a field.