lycopersici produces toxins that move through the plant resulting in leaf and fruit lesions.
#EARLY BLIGHT RESISTANT TOMATO VARIETIES CRACKED#
Vascular and pith tissue directly above and below the cankers may have brown streaks and become cracked and dry. Cankers will enlarge as the plant grows causing girdled stems, stem death, and plant collapse. Affected plants will often die, but if they do survive, their growth and yield will likely be reduced.Īlternaria stem canker is characterized by the formation of large, irregularly shaped, dark-brown to almost black cankers with light and dark concentric rings on stems near the soil line. Once the infected seedlings are planted in the field, the lesions will continue to enlarge around the stem and girdle the plants. As they enlarge, they will form circular or elongated lesions with or without pronounced concentric rings with light centers. In seedlings, collar rot stem lesions are small, dark, and slightly sunken. Symptoms and Signs Skip to Symptoms and Signs If greenhouse facilities have a history of collar rot, use preventative fungicides.įungicides do not efficiently control Alternaria stem canker on susceptible tomato varieties.Ĭan survive in soil between crop seasons and rotation out of tomato for 2-3 years can reduce disease.Ĭan survive indefinitely in the soil as a saprophyte and crop rotation is not effective. Primarily managed by planting resistant varieties. They are multicelled and 7-18 x 18-50 µm in size.Īlthough there are no collar rot resistant varieties, it is recommended to use varieties that are more tolerant to early blight. Spores formed in chains of 3-5, light olive brown to dark brown, “hand grenade” shaped with a shorter, beaked apical cell on the terminal end.
Spores are beaked, multicelled, dark brown to black, 12-20 x 83-117 µm in size, and can be borne singly or, less frequently, in chains of two. Collar rot versus Alternaria stem canker.Ĭauses large, irregularly shaped stem lesions with or without pronounced concentric rings.Ĭauses large, irregularly shaped stem lesions with pronounced concentric ringsĬaused by the fungal pathogen Alternaria linariae, which also causes early blight of tomato.Ĭaused by the fungal pathogen Alternaria alternata f. Humid climates and semiarid climates with frequent dews that provide high moisture (≥ 90% relative humidity) are conducive for both collar rot and Alternaria stem canker. When tomato transplants develop either collar rot or Alternaria stem canker in greenhouses or seedbeds, stem lesions can result in severe losses. However, if susceptible varieties are used, the disease can occur in North Carolina. This disease is not as much of a problem as many (or most) commercial tomato varieties have resistance to Alternaria stem canker. Symptoms of Alternaria stem canker can appear on the stems, leaves, and fruit of tomato plants. lycopersici and is primarily a problem of coastal-grown tomatoes in California. In contrast, Alternaria stem canker is caused by A. This phase of the disease is referred to as collar rot. However, if stem-infected tomato seedlings are set in the field, stem lesions will enlarge and eventually girdle the plants. Early blight is more commonly seen on field grown tomatoes and occurs on the foliage, stem, and fruit. linariae, that causes early blight of tomato. Collar rot is caused by the same pathogen, A. However, the concentric rings may not always be pronounced with collar rot. Both pathogens can cause large, irregularly shaped stem lesions with pronounced concentric rings. General Information Skip to General InformationĬollar rot and Alternaria stem canker of tomato are both caused by fungal pathogens in the genus Alternaria.
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