A water-soaked spot at the blossom end of tomato fruits is the classic symptom of blossom-end rot. This relatively common garden problem is not a disease, but rather a physiological disorder caused by a calcium imbalance within the plant. It can occur in pepper, squash, cucumber, and melon fruits as well as tomatoes.

Downy mildew is a disease of the foliage, caused by a fungus-like (Oomycete) organism. It is spread from plant to plant by airborne spores. It is a disease of wet weather as infection is favoured by prolonged leaf wetness.

Purple Blotch is caused by the fungus Alternaria porri. It is an important disease in warm, humid onion-growing regions around the world. Garlic and leeks may be affected as well as onions. Most long-day onion cultivars are susceptible, but sweet Spanish onions are generally more susceptible than common yellow cultivars. All short-day cultivars are susceptible.