BR - Black Rot
Scientific Name: Xanthomonas campestris
Type: Bacterium
Black Rot is a disease that affects the growth of arugula, broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustard, radishes, rutabaga, Swiss chard, tomatoes, turnips, and watercress. It survives in warm wet weather and affects cabbage throughout the United States. It is spread from one field to another field by water and wind. The bacteria can infect seeds and young seedlings. Young plants infected will turn yellow, drop lower leaves, and may die. Once the plant is infected there is no rescue treatment since the infection is systemic. Symptoms include the yellowing of the leaves in v-shape or wedge-shaped patches and blackening of the internal vein. Usually only a few of the outer leaves are affected. Since the disease is spread by water, anything that can be done to reduce leaf wetness will help reduce the spread of the disease. Water the plants in the morning, instead of the watering in the afternoon or night, so the leaves have time to dry before sunset. Increase space between the plants to maximize air flow and drying of the leaves. The disease is favorable when temperatures are 75-95 F and rain, heavy fogs, and dew are present. The bacteria does not spread when temperatures are below 50 F or during dry weather. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in the soil for two years. Treating the infected area with fungicides can help manage the disease. The primary source of bacteria of black rot is infested seeds and in infested transplants. The best option is to use disease resistant varieties, disease-free seeds, and disease-free transplants.
FY - Fusarium Yellows
Scientific Name: Fusarium oxysporum f. sp. conglutinans
Type: Fungus
Fusarium Yellows is a soil borne disease that affects the growth of broccoli, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, mustard, radishes, rutabaga, turnips, and watercress. It is a warm weather disease affecting cabbage throughout the United States. Cabbage and radish crops can be completely destroyed when the soil is infected with the disease. Symptoms include the curling of the leaves and the leaves turning a dull green to a yellowish-green color within a month after transplanting into the field. Young plants may be stunted, turn yellow, and die rapidly in warm weather. The leaves will turn yellow, then brown, wither, and eventually drop off the plant. The infected plants usually die within 2 weeks, other may die slowly. The surviving infected plants will have poor heads of cabbages that are non-desirable. The disease is sometimes confused with black rot, where the leaf veins turn black, rather than turning brown. The disease is favorable when temperatures are 80-85 F. Since the disease can survive in the soil for a long time, crop rotation, fungicide treatment, and destruction of crops, will have little impact once the soil is infected. The only option is to use disease resistant varieties.
PM – Powdery Mildew
Scientific Name: Erysiphe betae
Type: Fungus
Powdery mildew is a fungal disease that affects the growth of beets, cantaloupes & melons, cucumbers, peas, squash, Swiss chard, and tomatoes. The fungal disease may cause poor growth of the fruits in cucumbers if the infection is severe. The leaves of the cucumber begin to wither and then fall off prematurely. The disease usually affects older leaves. The leaves tend to turn a light green or a yellow green when infected. A powdery white or light gray color mold appears on the underside of the leaves. An odor similar to that of a musty basement is noticeable in fields with severe powdery mildew. The disease can spread rapidly under favorable conditions and infect the entire leaves within a week. The disease is favorable with long periods of dry weather, warm days, and cool nights, and fluctuations of day/night temperatures. The most favorable temperatures are 54-81 F and usually occur in early spring and autumn when moisture and humidity are very high. The disease can spread rapidly and can infect a field within 5 days. Fungicides for powdery mildew can help manage the disease. Good air circulation and increasing space between the plants can help control and prevent the disease. The best option is to use disease resistant varieties.