Most grains and pulses shipped from India are fumigated with phosphine gas, released from aluminium phosphide tablets or sachets. It is done either in a warehouse under gas-proof sheets or inside the loaded, sealed container, by a fumigation operator approved by India's plant protection authorities.
The aim is to kill live insects such as weevils, beetles and moths at every life stage. Fumigation does not remove insects that are already dead, and it does not undo damage already done to the grain.
The main methods
- Container fumigation: the fumigant is placed in the loaded container, the doors are sealed and the gas acts during the exposure period. This is common for export lots and often continues while the container moves to port.
- Stack fumigation: bags are stacked in a warehouse, covered with gas-proof sheets and sealed at the floor. This treats the lot before it is loaded.
- Methyl bromide: a fast-acting fumigant whose use is restricted under the Montreal Protocol. It is still used for some quarantine and pre-shipment purposes where an importing country requires it.
What makes fumigation work
Phosphine works slowly. It needs a gas-tight space, the right dose for the volume and enough exposure time, which is usually several days and longer in cool weather. A container with damaged seals or holes leaks gas and leaves survivors.
Temperature matters too. Insects are less active in the cold and take longer to kill. A good operator records the dose, the volume treated, the temperature and the exposure time. Ask to see these on the certificate, not just a stamp saying "fumigated".
After exposure, the space must be ventilated before people handle the goods. Residual phosphine is a safety risk for warehouse staff at destination, so many importers ask for a gas-free or degassing declaration.
Documents and destination rules
The operator issues a fumigation certificate. It is often needed alongside the phytosanitary certificate, which India's plant quarantine authority issues for plant products. The two documents are explained in what a fumigation certificate is and who issues a phytosanitary certificate in India.
Importing countries set their own rules. Some name the fumigant, the dose or the timing. Some accept phosphine; others require a specific treatment for certain goods. Check the current import conditions with your own plant health authority before you agree the contract, and write the required treatment into it.
Common problems to watch for
- Live insects found on arrival because the container leaked or the exposure was cut short.
- Certificates issued without the treatment actually being done.
- Fumigant residue packets left in the cargo, which some buyers reject.
- Fumigating goods that are already heavily infested, which kills insects but leaves frass, holes and damaged kernels.
- Phosphine residues in the grain above the limit set by your market, usually from poor ventilation or repeated treatment.
How we help
We check the lot for live insects and damage before loading, and we can attend the container fumigation and record the seal number. We also check that the certificate details match the container, dose and dates. To set this up for your next lot, ask for a free sourcing review.