Problems & Disease
Match what you see on the rope to the likely cause, then follow the recommended action.
Seaweed farming in Bangladesh uses no chemical pesticides or fertilisers. Every recommendation here is based on good farm practice and biosecurity.
Symptom
Fine hairy or slimy growth coating the rope and thallus. Growth slows and colour dulls.
Cause
Low water movement, over-crowded lines and delayed harvest.
What to do
- Shake and hand-clean lines every week
- Lower the stocking density on the rope
- Harvest on time rather than holding the crop
Symptom
Bitten or ragged thallus tips, and whole sections missing from the rope.
Cause
Rabbitfish, sea urchins, snails and crabs feeding on young thalli.
What to do
- Fit net guards around floating rafts
- Avoid rocky and reef-edge sites
- Harvest early where grazing pressure is heavy
Symptom
Branches turn white and hard, then break off in pieces.
Cause
Stress from sudden salinity, temperature or light change, followed by bacteria.
What to do
- Cut away and remove whitened parts before drying
- Move lines to deeper, steadier water (2–5 m)
- Use only healthy seed stock from an approved nursery
- Never use any chemical treatment
Symptom
Pale or bleached thalli within two days of heavy rain, then tissue breakdown.
Cause
Freshwater runoff pushes salinity below about 26 ppt.
What to do
- Act on the rainfall alert before the rain arrives
- Harvest mature lines ahead of a heavy rain forecast
- Do not seed new rope until salinity recovers
Symptom
A brown silt film on the thallus. Growth stalls and colour fades.
Cause
River runoff and stirred-up bottom sediment block the light.
What to do
- Raise lines closer to the surface
- Rinse the thalli during the weekly check
- Avoid plots near river mouths in high-runoff months
Symptom
Broken poles, snapped rope and rafts washed away.
Cause
Cyclones and pre-monsoon squalls in the Bay of Bengal.
What to do
- Follow the cyclone signal protocol in the alert
- Harvest early and lift rafts ashore
- Report losses in the app so the Department can record them