Bacterial Leaf Spot: This is something that is common in some gardens and that many new organic gardeners will recognize immediately. The leaves infected with this disease will have small, black or brown water-soaked spots. The spots will eventually dry up; crack, and leave holes and the infected leaves will often drop off and die prematurely.

This disease is common with tomatoes, peppers, and members of the cabbage family. The symptoms will often appear during wet weather and can be controlled by immediately removing infected leaves. It can be hard to keep up with the disease during wet weather but it can be done.

Late Blight: This disease most often affects tomatoes and potato plants later in the growing season. The disease will start out as wet grayish or greenish spots on the leaves and will progress into a white fungal growth that will form on the undersides of the leaves. There are some varieties and tomatoes and potatoes that are resistant to the disease. When these varieties are available select them regardless of the expense since you will benefit from a larger harvest. If you are unable to find a resistant variety remove and dispose of any infect parts of a plant. One way to help avoid this disease is to water plants early in the morning so that they have a chance to dry out completely during the day which will discourage fungus growth.

Common Rust: Rust will affect many vegetables so it must be watched for carefully. The following vegetables are commonly affected by vegetables:

Asparagus
Beans
Corn
Onions

The primary symptom of common rust is a reddish brown spot that appears to be powdery. These spots will usually appear on the leaves of the vegetables affected and will rub off when touch. Hand picking infected leaves will help reduce the spread of infection. Plants that are seriously infected should be completely removed and destroyed.

There are ways to avoid common rust completely. One way is to make sure all plants have good air circulation so avoid planting your seeds to close together since this will lead to crowded conditions. Also weed your garden often and prune plants to make sure plants continue to be well circulated.

Anthracnose: Organic vegetable growers in the United States will have to deal with anthracnose more often than organic vegetable growers in other countries. This disease occurs in warm, wet climates and will affect the stems, leaves, and fruits of the plants. Cucumbers, tomatoes, melons, and beans are the vegetables that are most often affected by the disease.

It will begin as small spots on various parts of the affected vegetable. Later pink spores will start to appear in the center of the spots. Water with a bit of lime juice sprayed on the leaf buds will help reduce the chances of this disease starting or spreading. Any seriously infected plants must be completely removed and destroyed.