This disease occurs mainly at the top of the leaves, the infection starts with whitish minute dots on the leaves with irregular chlorotic areas on tip portion of the leaves.
Circular to oblong concentric black velvety rings appear in the chlorotic area.
The lesions develop towards the base of the leaf.
The spots join together and spread quickly to the entire leaf area.
The leaves gradually die from the tip downwards.
Alternaria porri mycelium is branched, coloured and septate. Conidiophores arise singly or in groups. They are straight or flexuous, sometimes geniculate.
Disease free bulb should be selected for planting
Seeds should be treated with Thiram @ 4 g/kg seed.
The field should be well drained.
Three foliar sprayings with Copper oxychloride 0.25 % or Chlorothalonil 0.2 % or Zineb 0.2 % or Mancozeb 0.2 %.
