Septoria Leaf Spot Pest Control

Septoria Leaf Spot Pest Control Information

By Barbara Fahs, Garden Guides Contributor

About Septoria Leaf Spot

The fungus Septoria lycopersici is a common, destructive disease of tomato plants. It causes spotting of leaves, leading to dropping. Watch for small brown spots on lower tomato leaves, which turn yellow in time.

Prevention and Control

Because it's a fungus, Septoria spores require moisture to germinate and cause infection. Remove infected leaves from the garden at the end of summer, and the number of spores the following year will be fewer. Space susceptible plants to allow air circulation around them and allow leaves to dry off quickly after dew or rainfall. Don't overhead water, as this will promote leaf wetness and also splash spores from plant to plant.

Affected Plants

Septoria leaf spot commonly affects tomatoes but can also attack Rudbeckia, the lovely Black-Eyed Susan.


Septoria leaf spot is ugly to behold, but the damage is mostly cosmetic: infected plants normally bloom. Leaves that are infected can die sooner than healthy leaves, however. If you wait to treat this fungus, it might be too late for plants that are severely infested.

Natural Insecticides

Fungicide can help reduce the spread of the disease, but it won't cure infected leaves. Apply fungicide in early to mid June to help prevent infection and decrease symptoms. Continue applying fungicide throughout the growing season.

Other Methods of Control

In the fall, clean up your garden where you have grown Septoria-prone plants. Rotating crops also helps to reduce the available spores. Disease-resistant varieties of tomatoes have been developed; look for them in seed catalogs.

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