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BEST: Vegetable Diseases
Ashley Best
Ashley Best - photo by Special Photo

Vegetable gardening can be a rewarding but challenging endeavor, especially when dealing with various plant diseases that can affect the health and yield of your crops. The University of Georgia (UGA) Extension provides extensive resources on identifying, preventing, and managing common vegetable diseases. 

Common Vegetable Diseases and Their Management 

1. Blossom End Rot in Tomatoes: 

Blossom end rot is caused by a calcium deficiency, not a pathogen. It manifests as a soft, brown spot at the blossom end of the fruit. To prevent this, ensure consistent watering and add calcium to the soil using lime or gypsum before planting. Consider a soil test to have a pH of 6.2 to 6.8. Using calcium nitrate during the growing season can also help if symptoms appear​.

2. Late Blight: 

Late blight, caused by the fungus Phytophthora infestans, affects tomatoes and can rapidly destroy plants. It presents as yellowing and browning spots on leaves, stems, and fruit. Early treatment with fungicides containing chlorothalonil can help control this disease. Removing and properly disposing of infected plants is crucial to prevent spread.  

3. Powdery and Downy Mildew:


These fungal diseases affect a variety of vegetables including squash, cucumbers, and beans. Powdery mildew appears as gray-white patches on the upper leaf surfaces, while downy mildew shows light green to yellow patches on the underside. Removing affected plants and applying fungicides can manage these diseases​. Maintaining plant health through balanced nutrition and placing them in an open, sunny location can help reduce the impact of this and other diseases. 

4. Fusarium Wilt: 

Fusarium wilt, caused by Fusarium oxysporum, typically affects tomatoes, causing yellowing leaves that eventually turn brown after the plant starts to produce fruit. The fungus clogs the plant's vascular system, leading to wilting. This disease thrives in warm weather and is more severe in soils with nematode infestations. Crop rotation and using resistant varieties can help manage Fusarium wilt​. 

5. Southern Blight: 

Southern blight, caused by Sclerotium rolfsii, results in rapid yellowing and browning of leaves and stem rot at the soil line, often covered with white fungal growth and brown sclerotia. This disease prefers hot, humid conditions. Managing soil moisture and removing infected plants can help control it​. The pathogen can infect various host plants, but it most commonly affects tomatoes, peppers, and beans. Sclerotium thrives in hot weather, with infections occurring in humid and hot conditions (86 to 95 °F). Wet or poorly drained soils also promote the development of this disease. 

6. Root Rot: 

Root rot affects many plants, presenting as black, gummy roots and unhealthy foliage. It often results from poor soil drainage. Improving soil drainage and reducing watering frequency can help prevent root rot. 

Prevention Strategies 

1. Site Selection: 

Choose a garden site with good drainage and adequate sunlight. Avoid areas with poor air circulation to reduce humidity, which can promote fungal diseases​. Low spots or areas surrounded by vegetation will be more humid and encourage disease. 

2. Crop Rotation: 

Rotate crops to prevent the buildup of soilborne pathogens. Ideally, avoid planting the same or related crops in the same area more than once every three to five years​. Tomatoes, peppers and potatoes are all related crops and you should avoid planting them back-to-back in the same spot in the garden.  

3. Using Resistant Varieties:

Select disease-resistant varieties and purchase seeds from reputable sources. This reduces the risk of introducing diseases through seeds and transplants​. 

Proper Garden Management: 

Implement proper watering techniques, such as drip irrigation, to keep foliage dry and reduce disease incidence. Mulching can also help prevent soil splash and maintain soil moisture. Regularly remove weeds and plant debris, which can harbor pathogens​. 

Soil Testing and Fertility Management: 

Conduct soil tests to determine nutrient needs and maintain balanced fertility, which can help plants resist diseases better. Adjust soil pH and nutrient levels based on test recommendations​ (UGA Extension)​. 

By following these guidelines and staying vigilant, gardeners can effectively manage and prevent many common vegetable diseases, ensuring a healthy and productive garden. For more detailed information, visiting the UGA Extension website or contacting the Newton county extension office can provide additional resources and personalized advice.  

Ashley Best is the Agriculture and Natural Resources Agent with Newton County Extension Service. She can be reached at