Infected seedlings collapse at collar region and die in patches, entire clump dies in grown up plants.
Management
Drench with 0.2% copper oxychloride(2-3 litre/plant) and repeat this two times at monthly intervals.
As a bio-control measure,inoculate seedlings with native arbuscular mycorrhiza, Trichoderma and Pseudomonas fluorescens at the time of planting in the nursery and main field.
Dept of Agriculture Development 
SFAC Kerala