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Septoria Leaf Spot

Septoria Leaf Spot

Septoria lycopersici

Fungalalso: Septoria leaf spot of tomato

One of the most common leaf diseases of tomato, Septoria leaf spot speckles the lower leaves with small dark-bordered spots after the plant starts setting fruit. It rarely touches the fruit itself, but it can strip a plant of its leaves, cut yield, and expose fruit to sunscald. Wet, humid weather drives it.

🔎 How to spot it

Look for many small round spots, about one eighth inch across, with dark brown borders and tan to gray centers, scattered across the lower, oldest leaves. With a hand lens you can see tiny black specks, the spore-producing bodies, in the pale centers. Heavily spotted leaves yellow, then brown and drop. The disease moves steadily up the plant.

🥀 Damage it causes

Septoria defoliates the plant from the bottom up, and the loss of leaves weakens it, lowers yield, and leaves fruit exposed to sunscald. It seldom infects the fruit directly. A severe case can strip most of the foliage by late summer.

🔬 What causes it

The disease is caused by the fungus Septoria lycopersici, which overwinters on infected tomato debris and on related weeds such as nightshade. Spores are splashed onto the lowest leaves by rain and overhead watering. It is most active when temperatures run from about 68 to 77 F with high humidity and wet foliage.

🛡️ Prevent it

Rotate tomatoes to a new spot each year and clean up all plant debris at season end. Mulch to block soil splash, water at the base rather than overhead, and space and stake plants so leaves dry quickly. Prune off the lowest leaves and any early spotted leaves. Use resistant varieties where available and avoid working among wet plants.

🧯 If it is already here

At the first spots, pinch off and remove affected leaves; you can take up to a third of the lower leaves if you catch it early. Keep the foliage dry and mulched. If it keeps advancing, an approved organic fungicide containing copper, applied early and repeated through the season per the label, can hold it in check. Remove and destroy debris at the end of the year.

💡 Good to know

Septoria leaf spot is easy to mix up with early blight, but its spots are smaller and more numerous, with tan centers and tiny black dots, and they lack the target rings of early blight. Both begin on the lowest leaves after fruit set, and both are slowed by the same airflow, mulch, and rotation practices.

🌱 Plants it affects

112 plants in the library can be affected by this problem

Adirondack Blue PotatoAji Amarillo Pepper🥔All Blue PotatoAmethyst Falls WisteriaAmish Paste TomatoAnaheim PepperAnnabelle Smooth HydrangeaAnnual VincaArizona Sun Blanket FlowerBanana PepperBeauregard Sweet PotatoBecky Shasta Daisy🍅Beefmaster TomatoBetter Boy Tomato🍅Big Beef TomatoBig Boy TomatoBlack Beauty EggplantBlack Cherry TomatoBlack Krim Tomato🍅Box Car Willie TomatoBrandywine TomatoBrunneraCarolina JessamineCarolina Reaper PepperCascara SagradaCayenne PepperCelebrity TomatoCherokee Purple TomatoCleyeraClimbing HydrangeaCornelian CherryCrimson Cherry RhubarbCubanelle PepperDiabolo NinebarkEarly Amethyst BeautyberryEarly Girl TomatoEndless Summer HydrangeaEvergreen HuckleberryFairy Tale EggplantFeather Reed GrassFingerling PotatoFountain GrassFresno PepperGateway Joe Pye WeedGerman Butterball Potato🍅German Queen TomatoGhost PepperGoldflame SpireaGoldsturm Black-Eyed SusanGreen Bell PepperGreen Zebra TomatoHabanero PepperHummingbird SummersweetHungarian Wax PepperIndigo Rose TomatoItalian EggplantJalapeño PepperJapanese EggplantJapanese PierisJuliet Grape TomatoKellogg's Breakfast TomatoKennebec PotatoKobold Blazing Star🍅La Roma IV TomatoLemon Boy TomatoLily of the ValleyLimelight Panicle HydrangeaLingonberryLynwood Gold ForsythiaMajor Wheeler Trumpet HoneysuckleMedlarMoerheim Beauty Sneezeweed🍅Mortgage Lifter TomatoMr. Stripey TomatoNatchez Mock OrangeNorland PotatoOrange Bell PepperPadrón PepperPimento PepperPineapple TomatoPoblano PepperPurple Bell PepperPurple Coneflower🥔Purple Majesty PotatoQuaking AspenRed Bell PepperRed Pontiac PotatoRoma Tomato🍆Rosa Bianca EggplantRoyal Heritage Lenten RoseRusset Potato🍅Rutgers TomatoSalalSan Marzano TomatoScotch Bonnet PepperSerrano PepperSheffield Pink Garden MumShishito PepperSnow Queen Oakleaf HydrangeaSpeedwell

For educational and informational purposes only. Disease management advice is general guidance drawn from university cooperative extension sources; always identify a problem positively and read and follow the label on any product before use, especially around food crops, children, and pets.