Outbreaks of anthracnose cause incidental crop damage in all production areas.
Anthracnose can attack crops anywhere in the world. Isolates from spinach are recognised as a specialised form of this pathogen.
Symptoms and diagnosis
Leaf spots are small, watery lesions that can become chlorotic and eventually turn tan coloured. Plants may wilt as the lesions coalesce, causing the leaves to die. The presence of small black fungal bodies (acervuli) inside the circular leaf spots is a useful diagnostic feature enabling easy distinction of this disease from other leaf blights such as Stemphylium or Cladosporium.
Conditions for disease development
In most cases, the source of infection is infected crop residue, spontaneous emergence or infected seed. The spores are dispersed by rain splash and irrigation. Long wet periods are favourable for development. The disease can colonise necrotic or damaged tissue. The pathogen attacks a wide diversity of vegetable species, including onion and tomato. Dispersion between different host plants is therefore possible.
Impact and importance
Anthracnose can cause damage itself or be one of a combination of foliar blight diseases that cause smaller losses. The use of healthy seed should aid the control of this disease.