The fungus also causes many diseases like damping off, seedling blight, collar rot, stem rot, charcoal rot, basal stem rot, and root rot. If high temperature and humidity occur at this time, much of the foliage is killed. PROBLEMS: Tomatoes are susceptible to many pests and diseases such as blights, blossom end-rot, wilts, bacterial and viral diseases, tomato hornworms, aphids, beetles, and cutworms. Zones 9 & 10) Tomatoes Tomatoes ~ Seed Suppliers. Seeds infected prior to emergence rot and typically fail to produce a seedling. Printer Friendly Version of Disease Resistant Tomatoes, Text-Only Trader Joe's / ALDI's Exposé COVID-19 Tomato Disease Identification Chart Tomato Disease Abbreviations / Codes Cold-Adapted (Winter, U.S.D.A. Foliar Diseases of Tomato Steve Bost Professor Entomology and Plant Pathology EARLY BLIGHT, also called Alternaria leaf blight, is caused by the fungus Alternaria solani. The fungus causes a leaf blight and may cause seedling disease, collar rot, stem canker or fruit rot. Tomatoes can also be grown in containers at a minimum of 5 gal and 1-2 ft deep, one plant per pot. Lesions on the stems are similar to those on leaves and sometimes girdle the plant if they occur near the soil line (collar rot). Collar Rot and Alternaria Stem Canker of Tomato; Greenhouse Production. Post-emergence infections cause the seedlings to rot at soil line. If the seedlings do emerge, they are usually weak and lack vigour. Crop Protectants for Controlling Diseases of Vegetable Crops in Greenhouses; Good Agricultural Practices for Greenhouse Vegetable Crops; Foliar Fungal Diseases on High Tunnel and Greenhouse Tomatoes; Sclerotinia/White Mold/Timber Rot Management in Tomato High Tunnels It is the most common disease of tomatoes in Tennessee. Tissue surrounding the spots may turn yellow. This usually occurs within 2-4 weeks of emergence (or transplanting).