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7 Common Fungal Diseases in Home Garden Summer Vegetables

7 Common Fungal Diseases in Home Garden Summer Vegetables

By David B. Langston, University of Georgia, Bugwood.org – This image is Image Number 5076072 at IPM Images, a source for agricultural and pest management pictures operated by the Center for Invasive Species and Ecosystem Health, Colorado State University, USDA CSREES and the Southern Plant Diagnostic Network., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=6228070

Anthracnose (Anthracnose Colletotrichum spp.). This fungal disease usually effects pepper, tomato, sweet corn, legumes and cucurbits. It produces small round lacerations that start in the center and quickly spread to encase the fruit. The lesions can range from light brown to black in color. Grayish lesions can also appear sporadically on the stems and leaves of the plant.

Prevention is the key to controlling Anthracnose. Always purchase disease-free seeds and plants from a reliable source. A three-year crop rotation is also recommended for any planting area suspected of harboring the fungi.

By Rasbak – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=379630

Cercospora Leaf Spot (Cercospora beticola). Also known as Frogeye Leaf Spot, this disease is associated with Swiss chard, sugar and table beets, spinach and wild weeds such as pigweed, mallow, bindweed and lambsquarters (its cousin, Cercospora capsica, only attacks in pepper plants). The infection is usually found in host plants in southeastern parts of the U.S. This fungal infection produces small, moist lesions on the plant’s leaves, leaf stalks and stems. The lacerations colors can range from white, brown and red with dark purple borders. The lesions quickly grow larger and circular and as they mature, become brittle and crack.

The good news is, Cercospora infections are usually negligeable and require no treatment. However, after harvest the plants and debris should be removed and destroyed. Regular crop rotation should help prevent future occurrences.

By Jerzy Opioła – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=61137850

Fusarium Wilt (Fusarium oxysporum) distresses members of the Solanaceae family such as tomato, eggplant and pepper. It can also be associated with wild weeds such as crabgrass, mallow and pigweed. The infection causes wilting and yellowing of the plant’s top leaves. The disease thrives in overly moist or waterlogged soil. The infection can spread throughout the plant producing brown to reddish discoloration and which will eventually cause the plant’s demise.

Any infected plants should be removed and destroyed immediately. Always purchase disease free-seeds and plants from a reliable source and be sure to grow plants in well-draining soil.

By Clemson University – USDA Cooperative Extension Slide Series – http://www.forestryimages.org, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=22320810

Gray Leaf Spot (Stemphylium spp.) generally affects members of the Solanaceae family such as tomato, eggplant and pepper. The leaves of the diseased plants begin showing small brownish-red spots and as the lesions expand and mature, they become lighter in appearance. The larger lesions colors range from gray or white with brown-red edges. At that point, the leaves begin to turn yellow-brown and fall off.

When starting pepper plants indoors, make sure the area is well ventilated and kept away from tomatoes seedlings. If the disease shows up indoors, an application of fungicide may be warranted. If the transplants have been established outdoors, a fungicide may not be needed. However, after harvest, remove the plants and debris and destroy them, then rotate crops for the next three years.

By Pollinator at the English-language Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1293306

Powdery Mildew has several types of pathogens, with the two most common being Podosphaera xanthii associated with the cucurbit family (melons, luffas, winter & summer squash and watermelons) and Leveillula taurica associated with alliums, artichokes and sunflowers.  The pathogens create powdery mildew fungus in wet, humid conditions, poor air circulation and disperse by spores spread by the wind from other infected plants. It can also be spread by direct contact by handling diseased foliage. The mature leaves are typically affected first and exhibit areas of white, powder like growth on the top and underside. If left untreated, the spots on the leaves will begin to turn yellowish-brown, curl up and began falling of the plant.

If the disease becomes severe, a fungicide should be applied. After harvest, disposed of the plants and practice crop rotation and adequate plants spacing the following season.

By Lindsey D. Thiessen, Jason E. Woodward – Lindsey D. Thiessen et. al. "Diseases of Peanut Caused by Soilborne Pathogens in the Southwestern United States", ISRN Agronomy doi:10.5402/2012/517905, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=77111588

Southern Blight (Sclerotium rolfsii). This fungus is generally found in the soil, plant debris and hundreds of plants ranging from simple weeds to crops to ornamentals. It thrives in warm, humid conditions like those found in the southern United States, subtropical and tropical regions. The first signs of infection are moist spots and lesions on the leaves and stems of the plant. The fungus can quickly spread to other parts of the plant, including the roots and fruit, which can introduce other pathogens. Excessive heat and humidity help expediate the progression of the disease. The leaves and stems will begin to wilt, turn yellow/brown and thready fan-like mycelial can spread from the plant to the soil. The mycelia will also produce sclerotia (small brown/reddish/black particles). All infected plants should be removed carefully and immediately as well as 3 inches of soil from at least 12 inches beyond the infected area working the way from the outside towards the center. The plant material and soil should be bagged carefully and disposed of at a landfill only. Avoid contact with other plants or tools when removing to prevent spreading of the fungus. Allow crop rotation for three years with plants that are not susceptible to the disease such as large woody ornamentals.

To help prevent Southern Blight, check new plants thoroughly for any sign of the disease before planting and allow sufficient spacing between plants to promote good air circulation. If using a fungicide, it should be used as a preventive measure to ensure effectiveness. Make sure you read the list of ingredients and instructions very carefully.

By Howard F. Schwartz, Colorado State University, Bugwood.org – This image is Image Number 5365933 at Forestry Images, a source for forest health, natural resources and silviculture images operated by The Bugwood Network at the University of Georgia and the USDA Forest Service., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=11899325

Verticillium Wilt (Verticillium spp.) affects members of the cucurbit and the Solanaceae families at the onset of the disease, causing the lower portion of the plant’s leaves turn yellow and the plant to stop growing. Later, more leaves turn yellow, wilt and drop from the plant, which eventually dies. Once the disease has been introduced to a plant, it cannot be treated and should be removed and disposed of immediately.

A three-year crop rotation, solarization of soil and soil fumigation are preventive measures to help ensure the demise of the pathogen. or lessen the chances of an occurrence.

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