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Flowers, Fruits, and Frass

Local and statewide information on a variety of current topics for home gardeners and market growers.
Septoria Leaf Spot of Tomato Missouri Botanical
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Tomato Fungal Diseases Revisted


Fungal Diseases of Tomatoes

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Septoria Leaf Blight (Leaf Spot)

Septoria leaf spot is the most common of all the tomato diseases. The disease symptoms begin mid to late summer and start off as dark leaf spot the same as a pencil tip. The spots are surrounded by a yellow halo and some necrosis. The smaller spots advance to dark brown lesions with purple border and lighter colored centers. If a hand lens is used to examine the spot black spots indicate pycnidia are present. This fungal disease attacks leaves, stems and sepals and spares the fruit. The healthy looking fruit on diseased foliage can be a good indication Septoria leaf blight is the culprit. However, diseased and damaged leaves can cause fruit abortion and expose fruit to sunscald.

Early Blight (Leaf Spot)

Early blight's initial symptoms are small dark round spots (larger than Septoria Leaf Blight) that advance to reveal dark brown concentric lesions. The fungal disease causes yellowing, necrotic leaf edges and leaf drop. Leaves, stems and fruit are affected. The fruit has the same concentric ridges that look like leather. This disease starts on the seeds or transplants. In addition to tomatoes; tomatoes, peppers, and eggplant can be infected. Some tomato varieties, like the plum Juliet, have shown some tolerance. To find more resistant cultivars consult page 127 of the University of Illinois Extension Pest Management for the Home Landscape.

Leaf spot Control

University of Illinois recommends a 2 to 3 year crop rotation when the disease has been detected and to remove infected plants parts to prevent further spread. Good cultural practices of proper plant spacing and staking to ensure good air movement, reducing humidity by removing weeds and mulching the soil and not working in wet plants can reduce fungal disease pressures in your garden. Fungal pathogens can live in the soil for 3-4 years. All plant debris must be composted or tilled into the soil. All stakes and garden tools must be disinfected with alcohol or bleach solution.

Leaf spots can infect seeds. If a homeowner suspects seed contamination of Septoria Leaf blight, place in hot water for 30 minutes. A second seed treatment starts with a soak in 100 oz. +25 oz. of Clorox for 1 minute followed by a 5 minute rinse of plain water. When using pesticides to control fungal pathogens in tomatoes, be sure to follow directions on the label. To find fungicide recommendations consult page 130 of the University of Illinois Extension Pest Management for the Home Landscape. If fungicide sprays are going to be utilized use as a preventative treatment. Before deciding to do a curative spray understand that leaf loss can be 50% before there will be a loss in yield.

Anthracnose

Anthracnose is a fruit rot only. It infects healthy plants through soil and infected plant debris. The fruits will exhibit and sunken water spot that turns black and smooth unlike the fruit symptoms of Early Blight.




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