Alternaria alternata f. sp. lycopersici
Symptoms of Alternaria canker appear on stems, leaves and fruit. Large areas of the leaf lamina between veins is killed, leading to leaf curling and eventual death of the entire leaf.
Fungus overwinters in crop residue and is easily spread by wind. Wounding of young plants (by mechanical damage or pruning) provides an entry site for infection. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.