if you are going to contemplate using Fusilade on couch..
read this:
PERENNIAL GRASS WEEDS
Perennial grasses should be treated when growing actively. Spray young vegetative growth once it has sufficient leaf area to ensure good coverage and uptake of Fusilade – three to six leaves per shoot.
Perennial weeds growing from seed are easier to control. Established perennial grasses have many dormant buds on their underground rhizomes. Better long-term control of grass weeds will be achieved if these buds are activated before spraying.
Use SpraySeed® to eradicate existing growth and stimulate dormant buds of perennial grasses in orchards and vineyards.
Use Tryquat® to eradicate existing growth and stimulate dormant buds before sowing vegetables.
Perennial grass weeds that are reestablishing from fragmentation or desiccation should be treated when each new shoot has 3 to 6 leaves and is less than 2 months old.