Pests generally include aphids and mites. Downy mildew is the most common disease. Avoid the hot, moist conditions that favor spore germination. This is why it is better not to use sprinklers to water the plants. If you must sprinkle, do so in the morning so the leaves and shoots can dry.
Powdery mildew is another fungus.
Systemic or spray fungicides for downy mildew and sulfur-based fungicides for powdery mildew can be used as a last resort. Follow the directions carefully and wait the prescribed length of time between application and harvest. Verticillium wilt is a soil-borne fungal infection which may affect the plant differently over the years. There is no known control for verticillium wilt. Infected parts of the plant should be removed, and if the wilt persists over the years, remove the plants and start new plants elsewhere.