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John Fulton


John Fulton
Former County Extension Director



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In The Backyard

Horticulture columns and tips done on a timely basis
Septoria Leaf Blight on Tomato

Tomatoes

Posted by John Fulton -

Septoria leaf blight is attacking tomatoes again with a vengeance. For a review, septoria leaf spot can also affect plants at any stage of development. Numerous small, water-soaked spots first appear on the lower leaves. These spots soon become circular to angular with dark margins and grayish centers often bearing one or more tiny black bodies called pycnidia which are spore-bearing structures. Individual lesions are seldom more than ⅛ inch in diameter and are usually quite numerous on an infected leaf. Heavily diseased leaves turn yellow, wither and drop off in large numbers, starting at the base of the plant. Defoliation can be severe during prolonged periods of warm, wet weather.

As for what to do, here is the checklist: First, keep ripe fruits picked off the plants. Second, don't work around tomatoes when they are wet. Next, you can try and improve air circulation, but if your tomatoes are severely affected you won't want to lose any more leaves. And the final step for this year is to try a fungicide. Mancozeb is probably the recommended one, but it is very hard to find. The other options are Daconil and maneb, which are easier to find but probably won't give you as good of control. The final step for future years is to practice at least a three year rotation, with good sanitation in the garden.



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