10 Top Vegetable Diseases in 10 Minutes

10 Top Vegetable Diseases in 10 Minutes presented by Mark Gleason

Mark Gleason has been on the faculty at Iowa State University for 25 years, focusing on disease management for horticultural crops. On Saturday he gave a brief overview of the top ten diseases that affect vegetable crops.

1. Septoria leaf spot mainly affects tomato plants and is seen on the foliage as small, uniform brown spots sometimes associated with chlorosis (or yellowing). It is caused by the fungus Septoria lycopersici.

2. Bacterial spot is mainly seen on tomato transplants as small, circular, dark lesions found on foliage, which can develop into blighted areas on the leaves. It is caused by the bacteria Xanthomonas campestris and is easily transmitted by infected seed.

3. Bacterial canker is another bacterial disease common to the tomato, caused by the bacterium Clavibacter michiganensis and resulting in lesions on foliage or wilting. It is carried by infected seed and can be transported to the field on seedlings.

4. Cucurbit bacterial wilt is seen in cucurbits as the wilting of foliage and fruit. It is caused by the bacterium Erwinia tracheiphila and spread by the striped or spotted cucumber beetle.

5. Cucurbit downy mildew occurs in cucurbits as chlorotic lesions on foliage and gray “down” on the undersides of leaves. It is caused by the pathogen Pseudoperonospora cubensis and can be carried by the wind. It is essential to treat plants for downy mildew as soon as symptoms appear.

6. Cucurbit anthracnose appears on cucurbits as brown spots on the leaves and round lesions on fruit. It is caused by the fungus Glomerella lagenarium and is more common during periods of high precipitation.

7. Cucurbit powdery mildew is caused by the fungus Spaerotheca fuliginea or Erisyphe cichoracearum and appears as white, powdery fungal growth on the foliage of cucurbits. The fungal growth appears on the underside of leaves first, so it is important to regularly inspect your cucurbit crops.

8. Phytophthora blight affects cucurbits as well as eggplants, tomatoes, and peppers. Symptoms include damping-off of seedlings, leaf spots, stem rot, and fruit rot. It is caused by the soilborne pathogen Phytophthora capsici and can be controlled by crop rotation and adequate drainage.

9. Late blight occurs mainly in potatoes and tomatoes and can be seen as dark lesions or white spores on leaves or dark lesions on fruit. It is caused by the pathogen Phytophthora infestans, which is mainly transmitted via infected seed potatoes or the transmission of spores during wet conditions. It can be prevented by planting only certified healthy seed potatoes, destroying any potato plant residue left in the field after harvest, planting resistant cultivars, and the use of fungicides.

10. Damping off is a fungal disease that kills germinating seeds or young seedlings in the greenhouse. It is a soilborne fungus that can be prevented by using sterilized growing media, allowing for adequate drainage and air circulation, and encouraging the rapid germination and growth of seedlings.
(by Luke Freeman Senior at the University of Missouri, majoring in Sustainable Agriculture.)