ALS – Alternaria Leaf Spot
Scientific Name: Alternaria brassicicola, Alternaria cucumerina, Alternaria dauci
Type: Fungus
Alternaria Leaf Spot, also known Alternaria Leaf Blight, is a world-wide fungal disease that affects the growth of broccoli, Brussels sprouts, cabbage, cantaloupes & melons, carrots, cauliflower, cucumbers, kale, kohlrabi, pumpkins, radishes, rutabaga, squash, tomatoes, turnips, and watermelons. Symptoms may first develop on young plants where leaf spots develop, plants become stunted, and damping off may occur. Greenish-brown lesions appear on the leaves, and turn from dark brown to black spots. The disease may appear on the leaves at any stage and start off as concentric circles and mature to lesions with a bulls eye appearance. The leaves curl, turn yellow, wither, and eventually die off, and heavy infestations may cause complete defoliation. The infected plants should be removed to avoid further infestation. Increase space between the plants to maximize air flow and drying of the leaves. The disease is favorable when temperatures are 75-82 F and usually occur when moisture and humidity are very high. 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 8 years. Fungicides can help manage the disease. The best option is to use disease resistant varieties.
Ccu – Scab
Scientific Name: Cladosporium cucumerinum
Type: Fungus
Scab is a world-wide fungal disease that affects the growth of cantaloupes & melons, cucumbers, gourds, pumpkins, squash, and watermelons. Symptoms include pale green spots appear on the leaves which turn to gray spots and may have a yellow halo surrounding the lesion. The leaves become wrinkled and have ragged holes. The dead leaves crack and eventually fall off the plant. Cucumbers, pumpkins, and squash have sunken spots covered with greenish black velvety fungus. The fungus spores are spread by wind, insects, tools, and workers. The scab fungus overwinters on the seed, in crop debris, and in soil. The infected plants and vegetables should be removed, burned, or tilled in to avoid further infestation. The disease is favorable when temperatures are 59 - 77 F and usually occur when moisture and humidity are very high. Plan on using a 2 year crop rotation and avoid planting in the same location, year after year, as the disease can survive in over winter on crop debris. Proper tillage practices may be helpful in managing the disease. Control weeds, by tilling. Fungicides can help manage the disease. Use drip irrigation instead of overhead sprinklers if possible. Keep the day temperature in the 80's and have proper air circulation in greenhouses. The best option is to use disease resistant varieties.
CVYV – Cucumber Vein Yellowing Virus
Type: Virus - Ipomovirus
Cucumber Vein Yellowing Virus is a world-wide virus disease that affects the growth of cucumbers and watermelons. Symptoms include vein yellowing and vein clearing of the leaves and stunting of the plants. Light to dark green mosaic is observed on cucumbers. Watermelon splitting has been observed. The virus can reduce yields. It is spread by the whitefly. The virus overwinters in many perennial weeds. The infected plants should be removed to avoid further infestation. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year. Keep the fields weed free as infected perennials can harbor the virus. Proper tillage practices may be helpful in managing the disease. Insecticides for whiteflies may help control 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.