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.