Chestnut compound was first used for

Answer: Option C

Chestnut compound was first used for Damping off.
Chestnut compound was first suggested by Bewley in 1922 and is used especially to control damping-off diseases of seedlings.
The Chestnut compound contains two parts of copper sulphate and 11 parts of ammonium carbonate. The two substances are well powdered and thoroughly mixed and the dry mixture is stored in an airtight receptacle for 24 hours before being used.