Beetles found in stored grain at a mill

When beetles are visible moving on the outside of a bagged stack, the population inside it is considerably older than the sighting. Stored product insects breed within the grain itself, so what is on the surface is the part that has finished developing and left.

A surface treatment is the wrong tool here and it is worth saying why: it protects the outside of a sack and reaches almost nothing inside one. Fumigation is used because a gas moves through the sacking and through the commodity, which is where the insects are.

The practical work is mostly sealing. The stack is sheeted and sealed at every edge, treated, held for the exposure period, then ventilated before anyone handles the goods. A stack that lifts at one corner overnight loses concentration through that corner, and the grain under it is untreated while looking exactly like grain that was treated.

The other half of the job is the conversation about intake. A mill that treats the same store repeatedly usually has insects arriving with deliveries, and treating the symptom every quarter is more expensive than dealing with where it comes from.