How to Control Common Tomato, Pepper, Eggplant and Potato Diseases
Tomato, pepper, eggplant and potato, popular garden crops in the Solanaceae family of plants, are susceptible to several diseases that can diminish or completely ruin harvests. Some of those diseases damage fruit, while others devastate the foliage. In all cases, plant health and vigor is negatively affected.
Listed below are symptoms of the most common tomato, pepper, eggplant and potato diseases, and how to control them. Unless otherwise indicated, GardenTech® Daconil® Fungicide Concentrate, with the active fungal pathogen-fighting ingredient chlorothalonil, can be used to effectively treat the problem.
Disease: Anthracnose
Vegetables plants affected: eggplant, pepper and tomato
Symptoms: Damage due to anthracnose, a fungal disease, appears on ripening fruit in the form of dark, sunken lesions.1 The whole fruit eventually rots prematurely on the vine. The condition is common in regions that experience frequent high humidity, such as the southern United States.
Control: The spores from anthracnose live in soil, so avoid overhead watering, as this will cause the spores to splash onto the plant and infect it. Prevent healthy fruit from becoming infected by ensuring that it doesn't touch the soil. On infected plants, spores congregate in ripening fruit, so harvest as soon as the fruit is ready to eat, and then pick and throw rotting fruit away rather than letting it fall to the ground. Every three years, plant only non-Solanaceae vegetable crops in the planting bed for one season to help stop the disease cycle.2
Disease: Blight (Early)
Vegetables plants affected: eggplant, pepper, potato and tomato
Symptoms: Damage from early blight, another fungal disease, appears as circular brown spots on leaves and stems. Spots enlarge, creating concentric rings that resemble targets, and eventually take over the foliage, leading to defoliation. In severe cases, the plant loses all of its lower leaves and dies.3
Control: Early blight spores live in the soil, so avoid overhead watering to prevent infected dirt from splashing onto the foliage. Because blight thrives in humid, poorly ventilated areas, space plants at least 12 inches apart to allow for adequate air circulation. To help prevent the disease from spreading, promptly remove and discard all infected plants.3
Disease: Blight (Late)
Vegetables plants affected: eggplant, pepper, potato and tomato
Damage: The fungus that causes late blight is Phytophthora infestans, which means “plant destroyer" in Latin. This deadly disease led to the Irish potato famine of the 1840s. Damage from this plant annihilator appears as brown and black lesions on foliage, which quickly overtake the plant.4
Control: Late blight is a soil-borne fungal pathogen that is carried by wind, so remove and dispose of infected plants as soon as possible to help prevent the disease from spreading.5Also maintain a growing area free of weeds, as they can harbor the disease, and avoid overhead watering to help prevent infected soil from splashing onto foliage.2
Disease: Fusarium Wilt
Vegetables plants affected: eggplant, pepper, potato and tomato
Symptoms: Tomato and potato plants infected with Fusarium wilt first experience drooping foliage, followed by yellowing, wilting and eventual death of lower leaves. Infected pepper plants decay at the base of the stem first, followed by wilting of the lower leaves and soon the entire plant. Eggplant damage appears as wilting from lower to upper leaves, followed by plant collapse.
Control: There is no treatment for Fusarium wilt, so the best way for tomato growers to control the disease is to plant tomato varieties that resist the disease. Resistant plants carry an F (for Fusarium) on the label and on seed packages. Unfortunately, disease-resistant varieties of potato, eggplant and pepper plants don't exist. When the disease is first detected on those plants, remove and dispose of them. If Fusarium wilt continues to be a problem season after season in a certain area of the garden, avoid planting any plants from the Solanaceae family in that space for at least four years.6 Fusarium wilt can also be controlled by solarizing the soil for a season, which involves covering the soil with a clear plastic tarp for 4 to 6 weeks during the hottest time of the year. Trapped heat kills disease-causing pathogens in the top 12 to 18 inches of soil.7 Because cucumber beetles can spread the disease,9 keep them under control with Amdro® Quick Kill® Outdoor Insect Killer (RTS).
Disease: Gray Mold
Vegetables plants affected: eggplant, pepper, potato and tomato
Symptoms: Gray mold is a fungal condition that shows up initially as brown or gray circular spots on leaves, stems, flowers and fruit. Over time, the spots grow fuzzy mold.9 Flower buds develop abnormally, turn brown and fall off before blooming. When flowers do appear, they may be covered with brown spots.10
Control: Gray mold thrives in shade, so plant tomato, potato, pepper and eggplant in full sun.9 The disease also spreads quickly in poorly ventilated growing conditions, so provide good air circulation by spacing plants at least 12 inches apart. Prevent the spread of this disease by removing and disposing of infected plants as soon as the condition is detected. Also remove and discard any foliage and buds that have fallen to the ground. Gray mold spores live in the soil, so avoid overhead watering, which can cause soil to splash onto plants and spread the disease.10
Disease: Septoria leaf spot
Symptoms: Septoria leaf spot is a fungal disease that begins with yellowing of the lower leaves, progressing to form circular spots with dark borders and gray centers. Spots eventually reach one-eighth inch in diameter and borders become yellow. Black specks may develop in the center of the spots. In severe cases, leaves fall off, first at the base of the plant and then upward. At that point, without leaf protection, fruit is at risk of becoming sunscalded.11
Control: Many weeds harbor Septoria leaf spot, so weed your garden regularly. Avoid overhead watering, which can cause soil to splash onto plants and spread the disease. Help prevent the disease from returning year after year by removing and discarding tomato, pepper and eggplant plants immediately after they bear fruit,2 and by planting those crops in a different area of the garden each year.
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
Conclusion:
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.
GardenTech is a registered trademark of Gulfstream Home & Garden, Inc.
Daconil is a registered trademark of GB Biosciences Corp.
Lilly Miller and Amdro Quick Kill are registered trademarks of Central Garden & Pet Company.
Related Articles in Pest Management:
- What Is Integrated Pest Management?
- Fight Blight on Your Tomatoes
- Keep Your Garden Free From Fungal Disease
Sources:
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.
6. Sally A. Miller, et. al, "Fusarium and Verticillium Wilts of Tomato, Potato, Pepper, and Eggplant," The Ohio State University Extension.
7. J. J. Stapleton, et. al, "Soil Solarization for Gardens & Landscapes," University of California Statewide Integrated Pest Management Program, October 2008.
8. "Fusarium Wilt," Planet Natural.
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.
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