Top 5 Tomato Plant Diseases

By Amy Grant | June 16, 2018
by Amy Grant
June 16, 2018

Tomatoes are without a doubt one of the most popular crops grown in the home garden. Unfortunately, for every optimistic tomato grower, there are dozens of diseases and pests ready to crush hopes for a bumper crop of this luscious fruit goodbye. Here, in no particular order, is a list of the top 5 tomato plant diseases that strike fear into the most knowledgeable gardener.

1. Septoria Leaf Spot – A fungal disease, septoria leaf spot is one of the most common tomato leaf diseases. Symptoms appear as small, circular grey/white spots rimmed with a dark edge. The spots may be shot full of small BB sized black spots. Infected leaves turn yellow, resulting in defoliation. Control the disease by not overcrowding plants, avoid overhead watering, water in the morning, and treat signs of the disease with a fungicide.

2. FusariumFusarium wilt and Fusarium crown rot are both caused by the pathogen Fursarium oxysporum. Common to tomatoes, this fungal disease afflicts the plant’s vascular system. The roots of the plant become discolored, as the leaves yellow or brown and wilt. There is no fungicide available for control of this disease. Use F. oxysporum disease resistant tomatoes.

3. Early Blight – Also known as alternaria leaf spot, early blight is a fungal disease that results in leaf spots and stem and fruit lesions. The incidence of the disease rises when temperatures go up, resulting in brown/black target-like areas on mature leaves. Leaves may then yellow and drop. The best way to combat this disease is to practice excellent sanitation in the garden. Remove any plant debris, space plants properly, avoid overhead irrigation, and rotate tomato crops for at least 4 years. An application of sulfur may prevent new leaves from getting infected.

4. Bacterial Disease – A number of bacterial diseases is prevalent among tomatoes including bacterial speck, spot and canker. While slightly different symptomatically, all three bacterial diseases present as spots on leaves and fruit. The bacterium enters through wounds on the plant. To control these diseases, grow disease resistant plants and rotate crops. If applied at the first sign of infection, fixed copper sprays may reduce the spread of the disease.

5. Mosaic VirusMosaic virus attacks not only tomatoes but many other plants. While it does not kill the plant, it severely diminishes the quality and quantity of fruit. As the name suggests, the virus looks like a mosaic of green and yellow on the leaves and a mottling on the fruit. The leaves may also be deformed, looking much like those of ferns. Again, this virus enters the plant through wounds. Tobacco users can also transmit the disease. Plant resistant cultivars and do not replant in area that have been infected with the disease.

If you keep your garden and plants healthy by planting disease resistant varieties, spacing properly, mulching, irrigating with at least an inch (2.5 cm.) of water per week and rotating your tomato crops every 4 years, chances are good you will have little to no problem with disease.

Looking for additional tips on growing perfect tomatoes? Download our FREE Tomato Growing Guide and learn how to grow delicious tomatoes.

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