CLS – Cercospora Leaf Spot
Scientific Name: Cercospora asparagi, Cercospora beticola
Type: Fungus
Cercospora Leaf Spot is a world-wide fungal disease that affects the growth of asparagus, beets, carrots, corn, eggplants, peppers, soybeans, and tomatoes. It is the most destructive foliage disease of beets in Colorado, Nebraska, and Wyoming. Leaf spots occur on leaves. Symptoms include lesions of round or angular brown spots with green, brown, gray, or white centers. The leaves turn yellow, wither, and eventually die off and the whole plant becomes defoliated. The infected plants should be removed to avoid further infestation. The disease is favorable when temperatures are 55-65 F and usually occur between June and August when moisture and humidity are very high. Fungicides can help manage the disease. The best option is to use disease resistant varieties.
DM – Downy Mildew
Scientific Name: Peronospora farinosa, Peronospora parasitica, Pseudoperonospora cubensis
Type: Fungus
Downy mildew is a fungal disease that affects the growth of beets, broccoli, cantaloupes & melons, cauliflower, cucumbers, spinach, Swiss chard, and watermelons. Downy Mildew is most serious for cucumbers, which can drop dead in a week and stop producing any fruit to harvest. The disease affects both seedlings and mature plants.The infected leaves are retarded in growth, turn yellow then brown, and turn downward. A white to gray color mold appears on the underside of the leaves. The leaves will wilt and eventually die. The disease can spread rapidly under favorable conditions and infect the entire field. The infected plants should be removed and burned to avoid further infestation. The disease is favorable when temperatures are 58-72 F and usually occur in early spring and autumn in cooler weather when moisture and humidity are very high. Fungicides can help manage the disease. Good air circulation and increasing space between the plants can help control and prevent the disease, so use wide plant spacing to promote drying of the leaves. The best 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.
RZ – Rhizoctonia Root & Crown Rot
Scientific Name: Rhizoctonia solani
Type: Fungus
Rhizoctonia Root & Crown Rot is a world wide soil borne disease that affects the growth of beets. When the plant is infected, the leaves begin to wilt and the root system begins to rot. It can affect seedlings with damping-off problems, and the seedlings will wilt and often die. The crown on the beet root will rot, at or below the surface. Above ground symptoms include stunted leaves, dull leaf color, and a sudden wilting of the leaves. The leaves will turn yellow and eventually die. As the disease progresses, cankers and cracks may develop in the roots and a brown rotting may be seen in these cracks. Dark brown or black lesions may also be seen on the roots. In the advance stages of the bacterial root rot, a smell of fermentation will also be present. The disease is favorable when temperatures are 70-95 F and usually occur in poorly drained soil and where moisture and humidity are very high. Plan on using a 3 year crop rotation and avoid planting in the same infested location, year after year. Fungicides 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.