|Alternaria Leaf Spot||Purplish spots form on leaves and stems.||Alternaria||Avoid overhead irrigation. Apply fungicide registered for use on this crop.|
|Bacterial Leaf Spot||Small (2-5 mm) circular dead spots form on leaves and petioles. Spots have purple margins.||Pseudomonas tagetis||Destroy infected plants. Avoid overhead irrigation.|
|Botrytis Flower Blight||Flower parts brown and die. Gray masses of spores form on the infected tissue when wet.||Botrytis cinerea||Avoid overhead irrigation. Apply fungicide registered for use on this crop.|
|Fusarium Wilt||Seedlings are killed. In older plants, black streaks darken the vascular tissue up one side of the plant. Plants wilt. Roots on the greatly reduced root system are rotted. During wet weather, salmon-colored spore masses form on infected stems.||Fusarium oxysporum||Plant in potting mix free of pathogens. Destroy infected plants.|
|Leaf Burn||The tips and margins of leaves yellow and die.||Excess boron, manganese, or molybdenum||Measure and apply micronutrient solutions carefully. Manganese should not be above 55 ppm, molybdenum above 24 ppm, or boron above 3 ppm.|
|Septoria Leaf Spot||Oval to irregular gray to black spots with tiny dots peppering their surface (fungal fruiting structures) form first on lower leaves and then spread upward.||Septoria tageticola||Avoid overhead irrigation. Apply fungicide registered for use on this crop.|
Alternaria leaf and stem spot.
Prepared by Gary W. Moorman, Professor of Plant Pathology
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Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
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