Ten Suggestions for Vegetable Disease Management

Here are 10 suggestions to help keep your vegetable crop healthy.   

1.  Get plant problems accurately diagnosed. Before deciding on a control measure, are you sure you know what the problem is? The optimum control of downy mildew on cucumbers, for example, requires specialized fungicides. On the other hand, no amount of fungicide will control blossom-end rot on tomatoes, which is a calcium deficiency. The Purdue Plant and Pest diagnostic lab can be contacted here. A library of vegetable disease photos can be found here. 
2. Scout your fields for disease or disease-like symptoms. To determine when you need to send in samples for diagnosis, you must scout your crops. Develop a schedule, say, once a week, to scout your fields or greenhouses. In a field, use a zig-zag pattern as you cross the field (yes, it helps to get out of the pick-up!). Scout each field separately and scout varieties in the same field separately.  Keep records.   
3. Physically separate vegetable transplant varieties. Let’s imagine that you grow 6 tomato varieties from transplant greenhouse to the field. If one of the varieties becomes diseased, it may quickly spread to all varieties. Therefore, physically separate the varieties so that overhead watering of the transplants in the greenhouse doesn’t spread the disease from one variety to the others. For the same reason, separate the same variety if there are different seed lot numbers. The same advice holds for other vegetable crop transplants. Be sure to scout varieties separately whether as transplants or as mature plants in the field. 
4. While we are discussing greenhouse transplant production, let me emphasize sanitation. If you are starting transplants from seed, purchase new trays each year or clean and sanitize the trays with bleach, quaternary ammonium, a chlorine solution, or a peroxide product. Use new soilless media each year. Avoid dumping the media on unsanitized surfaces. Clean and sanitize all tools and surfaces that the transplants may come into contact with.
5. Avoid fields with a history of disease, particularly soilborne disease. Disease organisms that survive in soil, soilborne pathogens, may survive for years in a field without a host. An example would be Fusarium wilt of watermelon. Another disease caused by an organism that may be soilborne is Phytophthora blight, which may affect many crops. In addition to avoiding fields with a history of Phytophthora blight, it is important to avoid areas of the field with poor drainage since this disease thrives in water.
6. A practice known as rogueing aims to remove diseased plants to slow the disease’s spread. An article describing this practice in more detail can be found here.
7. Be smart about applying fungicides. Apply fungicides before a disease is observed, apply before a rain event, pay attention to fungicide modes of action, etc. This article describes fungicide application in much more detail.
8. Crop rotation and fall tillage are critical to vegetable disease management. This table describes many common crops and diseases and the crop rotation and tillage suggested.
9. Use resistant or partially resistant varieties when possible. Your seed company should be a good source of information about disease resistance. The table in #8 above also has information about disease resistance.
10. A good vegetable farm will be well organized. Written records are kept and ordered. Tools and equipment are accessible, arranged, and clean. Buildings are kept clean and well-ordered. Surfaces are clean if not sanitized. Think of your operation as a restaurant-one at which you would feel comfortable dining.