Eggplant Anthracnose – Eggplant Colletotrichum Fruit Rot Treatment
By: Bonnie L. Grant, Certified Urban Agriculturist
Anthracnose is a very common vegetable, fruit and occasionally ornamental plant disease. It is caused by a fungus known as Colletotrichum. Eggplant colletotrichum fruit rot affects the skin initially and can progress to the interior of the fruit. Certain weather and cultural conditions can encourage its formation. It is very contagious, but the good news is that it can be prevented in some cases and controlled if confronted early enough.
Symptoms of Colletotrichum Eggplant Rot
Colletotrichum eggplant rot occurs when leaves are wet for a long period of time, usually around 12 hours. The causal agent is a fungus that is most active during warm, wet periods, either from rainfall in spring or summer or from overhead watering. Several Colletotrichum fungi cause anthracnose in a variety of plants. Learn the signs of eggplant anthracnose and what you can do to prevent this disease.
The first evidence of this disease in eggplants are small lesions on the skin of the fruit. These are usually smaller than a pencil eraser and circular to angular. Tissue is sunken around the lesion and the interior is tan with fleshy ooze which is the spore of the fungus.
When fruits are extremely diseased, they will drop from the stem. The fruit becomes dry and black unless soft rot bacteria get inside where it becomes mushy and decays. The entire fruit is inedible and the spores spread rapidly from rain splash or even wind.
The fungus that causes eggplant colletotrichum fruit rot overwinters in leftover plant debris. It begins to grow when temperatures are 55 to 95 degrees Fahrenheit (13 to 35 C.). The fungal spores need moisture to grow. This is why the disease is most rampant in fields where overhead watering occurs or warm, rainfall is persistent. Plants that retain moisture on fruit and leaves for a long period promote growth.
Infected plants spread the disease. The eggplant anthracnose can also survive in seeds, so it is important to select disease free seed and not to save seed from infected fruit. Disease symptoms can occur on young fruit but are more common on mature eggplant.
In addition to careful seed selection, removal of the previous season’s plant debris is also important. Crop rotation can also be helpful but be wary of planting any other plants from the nightshade family where infected eggplants once grew.
Application of fungicides early in the season can help prevent many outbreaks. Some growers also recommend a post-harvest fungicide dip or a hot water bath.
Harvest fruits before they are overripe to prevent the spread of the disease and remove any that show signs of infection promptly. Good sanitation and seed sourcing are the best methods of colletotrichum control.
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Colletotrichum species, particularly, Colletotrichum capsici, and Colletotrichum gloeosporioides. The sexual state is Glomerella cingulata (see Fact Sheet no. 177).
Worldwide. Colletotrichum capsici: Asia, Africa, North America, Europe, Oceania. It is recorded from Cook Islands, Fiji, Niue, Papua New Guinea, Samoa, Solomon Islands, and Tonga. Colletotrichum gloeosporioides: Worldwide. It is recorded from American Samoa, Australia, Cook Islands, Federated States of Micronesia, Fiji, Kiribati, Marshall Islands, New Caledonia, Niue, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalu, and Vanuatu (and more).
Anthracnose on tomatoes
One of the most common fruit rots of tomato, especially in vegetable gardens, is caused by several species of the fungus Colletotrichum. Ripe and overripe fruit are especially susceptible but the pathogen can infect green fruit with symptoms not developing until fruit begin to ripen. Spots on fruit initially are small, circular, and depressed. They can enlarge considerably over time, and may develop concentric rings. The center of anthracnose spots become dark as the fungus produces spore-containing structures (microsclerotia and acervuli).
Masses of pink to orange colored spores are released from these structures when weather is wet or humid. These spores are dispersed to other fruit by splashing water. Eventually the entire fruit will rot, especially when there are several anthracnose spots or decay organisms enter the diseased tissue. Fruit nearest to the ground are most likely to be affected. The fungus can also infect roots.
Manage anthracnose by controlling sources of the pathogen, minimizing the opportunity for dispersal of the pathogen, reducing favorability of environmental conditions for disease development, and applying fungicides. There are no resistant varieties.
The spore-containing structures provide a means for the causal fungus to survive between crops. Consequently, important practices for managing anthracnose include rotating where tomatoes are grown. Not growing tomatoes or other solanaceous plants (especially potato) in the same area for 3 to 4 years is ideal. A practice that can be implemented in a small garden is removing affected fruit rather than letting them drop to the ground.
The pathogen can also be seed-borne, Therefore seed should not be saved from diseased fruit.
Covering the ground with black plastic mulch, straw, or other material provides a barrier between the pathogen in the soil and fruit. Trellising plants increases the distance between the fungus in the soil and fruit, plus air circulation will be improved enabling plant tissue to dry more quickly.
Many fungal pathogens need plant tissue to be wet in order to infect. Practices to minimize the length of time that fruit will be wet from rain or dew include trellising, locating tomatoes where there is good air movement and no shade, and orienting rows parallel to the predominant wind direction. Providing water to the base of plants rather than using a sprinkler not only avoids wetting fruit, but avoids the opportunity for splash dispersal of the pathogen.
Pick fruit as soon as it is ripe to minimize the time for anthracnose to develop, but note that development of symptoms is not completely prevented by taking fruit from plants to drier, protected, indoor conditions.
Summary on managing anthracnose in the garden: Don’t save seed from fruit in a planting where anthracnose occurred. Don’t plant tomatoes where you did the previous year, at least 2 years best. Plant where tomatoes will receive full sun no shade from trees, etc. as this will increase humidity. Trellise plants so fruit are far from soil and plants will dry more quickly after rain. Cover soil surface with straw, grass clippings, or plastic mulch. Space plants well to minimize humidity. Water base of plants rather than using sprinkler system that causes splashing water on fruit. Many pathogens thrive when watering is done in early morning such that the period of time leaves and fruit are wet is extended. And watering in early morning can cause pathogens to be splashed dispersed to healthy plant tissue. Many pathogens produce spores over night when it is dark and humidity is high. Remove any volunteer tomato seedlings. Promptly harvest ripe fruit. Note that symptoms of anthracnose can develop as fruit sits after harvest, so use promptly. Remove from the garden any fruit that rot. Do not compost fruit tissue with anthracnose.
Symptoms developed on fruit in following two photographs a few days after harvest while in a house.
Disease: Verticillium Wilt
Vegetables plants affected: eggplant, pepper, potato and tomato
Symptoms: Symptoms of Verticillium wilt generally don't appear until after the plant has produced a heavy crop or unless the weather is dry. Bottom leaves become pale, leaf edges turn brown, and the plant eventually defoliates. Sometimes symptoms appear only on one side of the plant. Infected plants usually survive, but low yields are produced and growth is stunted. 6
Prevention: There is no treatment for Verticillium wilt, so the best way to control the disease is to plant tomato varieties that resist the disease. Resistant plants carry a V (for Verticillium) on the labels and on seed packages. Unfortunately, Verticillium wilt-resistant varieties aren't available for potato, eggplant and pepper plants. So control spread of the disease by removing and disposing of infected plants when the wilt is detected. If the disease continues to be a problem in a specific area of your garden season after season, avoid planting any plants from the Solanaceae family in that space for at least four years, or solarize the soil for one planting season. 6
Healthy plants have a better chance of resisting disease. 12 Give your vegetable garden full sun, sufficient water and keep it nourished with high quality fertilizer, such as Lilly Miller® All Purpose Planting & Growing Food 10-10-10.
Always read the product label and follow the instructions carefully.
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Related Articles in Pest Management:
1. "Anthracnose Colletotrichum orbiculare," Texas A&M Agrilife Extension, July 2009.
2. John P. Damicone and Lynn Brandenberger, "Common Diseases of Tomatoes," Oklahoma Cooperative Extension Service.
3. Brian Hudelson, "Early Blight," University of Wisconsin-Extension, March 10, 2012.
4. Schumann, G.L. and C. J. D'Arcy, "Late blight of potato and tomato," The American Phytopathological Society, 2005.
5. Abby Seaman, et. al, "Late Blight: A Serious Disease of Potatoes and Tomatoes," Cornell University Integrated Pest Management Program.
7. J. J. Stapleton, et. al, "Soil Solarization for Gardens & Landscapes," University of California Statewide Integrated Pest Management Program, October 2008.
9. Joey Williamson, "Gray Mold (Botrytis Blight)," Clemson Cooperative Extension, February 2015.
10. "Botrytis Blight," Missouri Botanical Garden.
11. Howard F. Schwartz and David H. Gent, "Septoria Leaf Spot," University of Wyoming, University of Nebraska, Colorado State University and Montana State University, April 1, 2007.
12. Simeon Wright and Christopher Starbuck, "Preventing and Managing Plant Diseases," University of Missouri Extension, April 2008.