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.
Damage
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.
