Baxter County Master Gardener Program • University of Arkansas System • Division of Agriculture • © 2013 BCMG
The Plant Health Clinic has received numerous samples of tomatos with severe leaf damage. Septoria Leaf Spot caused by Septoria lycopersici is one of the most damaging diseases of tomato foliage. Septoria is favored by warm temperatures and high humidity.
Symptoms of Septoria generally appear on the lower leaves after the first fruit sets. Lesions are circular, about 2.6mm in diameter, with dark brown margins with tan to gray centers. A narrow yellow halo may often be observed around the lesion. Small black fruiting bodies of the fungus (pycnidia) may be observed in the centers of the lesions using a hand lens. Lesions may coalesce to form large blighted areas. Foliage turns yellow, then brown and dry. The plant has an almost burned appearance. There are no resistant cultivars available.
Control measures include crop rotation with a non-host, control of weeds in tomato crops, removal of all crop debris, and avoidance of night watering and overhead irrigation. Protective fungicides at regular intervals during the growing season will be necessary for most growers. Quadris, Cabrio, Flint, Bravo, Mancozeb, and Gavel are labeled for Septoria leaf spot control. Homeowners may use Ortho Garden Disease Control, or Fertilome Liquid Fungicide, or Bonide Fung-onil Multipurpose Fungicide Concentrate, or Garden Tech Daconil Fungicide Concentrate, or Bonide Mancozeb Flowable w/Zinc, or Hi-Yield Maneb Garden Fungicide, or Green Light Tomato and Vegetable Spray. Organic Gardeners may try Bayer Advanced Natria Disease Control, or Bonide Liquid Copper Fungicide Concentrate, or Kaligreen, or Bonide Remedy, or Bonide Copper Dust, or Hi-Yield Bordeaux, or AgraQuest Serenade.
University of Arkansas Plant Health Clinic Newsletter