ALS – Angular Leaf Spot
Scientific Name: Pseudomonas syringae pv. lachrymans
Type: Bacterium
Angular Leaf Spot is a world-wide bacterial disease that affects the growth of cantaloupes, melons, cucumbers, and squash. It can also affect strawberries. It is caused by the Pseudomonas syringae pv. lachrymans bacteria. Angular leaf spot thrives in warm, humid conditions. Symptoms may first develop on young plants where small angular spots develop that turn brown or straw-colored. Under humid conditions, milky white liquid may appear on the spots. The disease can also affect the stem and cause the fruit to rot. The disease expands during rainy weather and temperatures of 75 to 82 degrees F. The infected plants should be removed to avoid further infestation. Avoid working among plants when foliage is wet and use overhead irrigation when possible. 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 2 years. Pesticides 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.
CMV – Cucumber Mosaic Virus
Type: Virus - Potyvirus
Cucumber Mosaic Virus is a world-wide virus disease that affects the growth of cantaloupes & melons, cucumbers, eggplants, gourds, peppers, pumpkins, spinach, squash, tomatoes, and watermelons. Symptoms include stunted or dwarfed plants, mottling, yellowing, distortion, and wrinkling of the leaves with the edges curling downward, and reduced growth rate and yields. The symptoms on leaves known as "shoestring" effect causes young leaves to appear narrow. The leaves will die and fall off, leaving part or most of the plant bare. The virus causes cucumbers to turn pale and gray, become bumpy and oddly shaped, and have a bitter taste. The virus causes peppers to have severe leaf damage with mosaic and necrotic rings. The peppers may have rings and spots. Tomato plants are usually stunted and have poorly shaped leaves and can cause partial or total crop loss. Plants infected with the virus have little or no marketable fruit. The virus can reduce yields and fruit quality. It is spread by aphids, seeds, and weeds. The virus overwinters in many perennial weeds. The infected plants should be removed to avoid further infestation. This virus cannot live in extremely dry conditions. The disease is favorable when temperatures are 79-89 F when aphid infestation is great. Symptoms usually begin to show in June. 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 aphids are of limited value to control the disease. Spraying the tomato plants with mineral oil can delay the aphids from spreading the virus.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.
PRSV – Papaya Ringspot Virus
Type: Virus - Potyvirus
Papaya Ringspot Virus is a virus disease that affects the growth of cantaloupes & melons, cucumbers, pumpkins, and squash. Papaya ringspot virus is primarily a problem in the southern and western regions of the United States. Symptoms include yellowing and vein-clearing of young leaves, yellow mottling of the leaves, distinctive ringspot patterns on the fruit, and fruit quality, particularly flavor, is adversely affected. The infected plants should be removed to avoid further infestation. It is only spread by aphids. There is no cure for papaya ringspot disease. Insecticides for aphids are of limited value to control the disease. The best option is to use disease resistant varieties.
TLS – Target Leaf Spot
Scientific Name: Corynespora cassiicola
Type: Fungus
Target Leaf Spot is a world-wide fungal disease that affects the growth of cucumbers. Symptoms include lesions of angular yellow spots on leaves. The spots become larger and circular with light brown center and dark brown borders. The spots eventually turn gray and the leaves will eventually die off and the whole plant becomes defoliated. The most damaging aspect of scab is on the fruit. Small sunken spots appear on the cucumbers. The infected plants should be removed to avoid further infestation. The disease is favorable when temperatures are 77 - 85 F when moisture and humidity are very high. The fungus can remain on infected plants and weeds for 2 years. Fungicides can help manage the disease. The best option is to use disease resistant varieties.
ULS – Ulocladium Leaf Spot
Scientific Name: Ulocladium cucurbitae
Type: Fungus
Ulocladium Leaf Spot is a world-wide fungal disease that affects the growth of cucumbers. Symptoms include lesions of reddish brown spots on leaves. The spots become larger and circular to irregular in shape with the center is beige to brown surrounded by a dark brown ring and a brown halo. The infected plants should be removed to avoid further infestation. The disease is favorable when temperatures are 70 - 81 F in early to mid-August 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 over winter on crop debris and soil for 2 years. Fungicides can help manage the disease. The best option is to use disease resistant varieties.
WMV – Watermelon Mosaic Virus
Type: Virus - Potyvirus
Watermelon Mosaic Virus is a virus disease that affects the growth of cantaloupes & melons, cucumbers, gourds, pumpkins, squash, and watermelons. Watermelon mosaic virus is primarily a problem in the southern and western regions of the United States. Symptoms include stunted or dwarfed plants, yellow or light green mottling, blistering, marginal yellowing, leaf distortion, and reduced growth rate and yields. Losses of 50 percent or more in yield and fruit quality may occur. The fruit frequently show color breaking and warts. It is only spread by aphids. Symptoms usually begin to show in June. Plan on using a 3 year crop rotation and avoid planting in the same location, year after year. Plastic mulches have been shown to reduce losses. Insecticides for aphids are of limited value to control the disease. The best option is to use disease resistant varieties.
ZYMV – Zucchini Yellow Mosaic Virus
Type: Virus - Potyvirus
Zucchini Yellow Mosaic Virus is a world-wide virus disease that affects the growth of cantaloupes & melons, cucumbers, gourds, pumpkins, squash, and watermelons. Symptoms include stunted or dwarfed plants, mottling, yellowing, distortion, blistering, and wrinkling of the leaves, and reduced growth rate and yields. The virus can cause total crop lose. The symptoms on leaves known as "shoestring" effect causes young leaves to appear narrow, and fern-like appearance of the leaves. The virus causes cucumbers to become bumpy and oddly shaped, and have a bitter taste. Cantaloupes & melons and watermelons are malformed and often develop deep cracks. Squash and pumpkins can develop knobby areas. Plants infected with the virus have little or no marketable fruit. The virus can reduce yields and fruit quality. It is spread by aphids and seeds. 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. Proper tillage practices may be helpful in managing the disease. Insecticides for aphids are of limited value to control the disease. Using transparent or silver plastic mulches have been shown to repel aphids and delay the virus from spreading. Ladybird beetles can be effective at naturally controlling aphid populations. The best option is to use disease resistant varieties.
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