|Flower failure||Plants do not flower but otherwise appear healthy.||Not a disease||Divide and replant to alleviate overcrowding.|
|Foliar nematode||Brown areas on the leaf are restricted in shape by leaf veins. These angular spots are usually seen on the lower leaves.||Aphelenchoides||Remove the leaves showing symptoms. Thin dense clumps to improve air circulation and irrigate in a manner that keeps water off the foliage.|
|Leaf scorch||Margins of leaves turn red to reddish-brown.||High temperatures, dry soil, windy conditions.||Move the plants to a shady, moist location. Note that leafhopper feeding can also cause leaf tips to redden and brown.|
|Leaf spot||Well defined dead spots form on leaves. Under ideal conditions of wet weather, spots merge and result in large dead areas on the leaf.||Cercospora||When watering plants, do so in a manner that keeps water off the foliage. Apply a fungicide to protect plants.|
|Powdery mildew||White fungal growth develops on the upper surface of leaves.||Erysiphe polygoni||Apply a fungicide to protect plants.|
|Root knot nematode||Galls form on roots and plants may be stunted.||Meloidogyne||Remove infected plants. Cultivate the area to remove all plants and leave the soil bare for a growing season before replanting.|
|Virus||Plants are yellowed but roots appear healthy.||Tobacco ringspot virus||Remove infected plants.|
|Wilt||Plants are stunted or wilted and have brown sunken dead areas on the stem near the soil line.||Rhizoctonia or Fusarium||Remove affected plants.|
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