Preparing a grain store for harvest

Preparing a grain store properly means five jobs, done in order, weeks before the combine moves: empty it completely, clean it top to bottom, repair and proof it, set bait and monitoring before grain arrives, and write down what you did. None of it is complicated. Most of it is dull. All of it is cheaper than the alternative, which is finding weevils in a heap in November or failing a store inspection with 600 tonnes already on the floor.

The mistake isn't usually doing the jobs badly — it's doing them the week before harvest, in a rush, around a shed that still has last year's tailings in the corner and a seed drill parked on the pad.

Empty it completely — and mean completely

Half a tonne of old grain swept into a corner is not an empty store. It's a breeding colony with a roof over it. Grain weevils and saw-toothed grain beetles overwinter in exactly this sort of residue — in floor cracks, under duct covers, inside elevator boots and auger tubes — and they will walk straight into the new crop the day it's tipped.

So the first job is genuine emptiness: every last bit of old grain out, including the awkward stuff. The pit sump. The dead spots under the intake. The ledge above the grain walling where dust and kernels have sat since 2019. If the shed doubles as machinery storage over winter, the kit comes out too, because you can't clean a floor you can't see.

The clean-down, high to low

Dust falls. Clean from the top down or you'll do the floor twice:

Roof steelwork, purlins and ledges first. Brush or blow down the accumulated dust and cobwebs. This is where mites and beetle eggs sit out the summer.
Walls and grain walling, paying attention to joints and any gap behind panels.
Fixed handling kit — elevators, conveyors, augers, the drier itself. Open inspection hatches and clean inside. A conveyor that ran wet barley last September is a reliable source of this year's infestation.
The floor last, including duct covers lifted and the ducts themselves swept or vacuumed. On-floor drying ducts full of old grain and dust are both a pest reservoir and an airflow restriction.
The pit, if you have one, right to the bottom. Pits collect everything and get cleaned least.

A decent industrial vacuum beats a broom for most of this — sweeping moves dust around; vacuuming removes it. Where a store has any history of insect trouble, a residual insecticide treatment on the cleaned surfaces is worth considering, applied per the label and recorded. Our guide to grain store insects and mites covers what you're actually defending against.

Repairs and proofing

While the store is empty is the only realistic time to fix it. Walk it with a critical eye — ideally on a wet day, because rain ingress announces itself:

Roof and gutters. One dripping sheet joint over a heap will make a wet column that heats. Follow any floor staining upwards.
Doors. They should shut tight enough to keep birds and weather out. Brush strips and door seals are cheap; a pigeon living in the shed all winter is not.
Bird proofing. Netting over vents and openings. Bird droppings in grain are a contamination issue buyers and assurance schemes take seriously.
Vermin proofing. Gaps at the base of cladding, holes around service entries. Rats want about 15mm; mice less.
Floor cracks. Fill them. Cracks harbour insects and defeat the clean-down.

Bait points and traps go in before the grain does

Set your rodent bait points and insect monitoring traps once the store is clean and still empty — not after filling, when half the floor is inaccessible under 500 tonnes of wheat.

For rodents: numbered, tamper-resistant bait stations around the perimeter, mapped, and checked on a routine. For insects: pitfall traps in the (empty) store tell you whether the clean-down worked before you commit grain to it, and probe traps in the heap afterwards catch a build-up long before a buyer's intake does.

The point of doing it early is baseline. A trap catching beetles in a supposedly clean store in July is a problem you can still fix cheaply. The same beetles found by a merchant's sieve in a 29-tonne load in January are a rejection.

Fans and driers: serviced in June, not tested in August

Harvest is a bad time to discover a seized fan bearing. Get ventilation fans, drier burners, temperature sensors and moisture meters serviced or at least run up in June or early July while there's still time for parts. Check duct covers fit, that the drier's controls do what they claim, and that any temperature monitoring kit actually reads.

The same logic as the rest of the pre-harvest checklist: everything that will be needed at 9pm on a hot Saturday in August should be proven working in June.

Write it all down

Assurance schemes ask for evidence, not intentions. Record the clean-down date, who did it, what was cleaned, any treatments used (product, rate, operator), bait point checks, and proofing repairs. A simple dated log is fine — what matters is that it exists and is current when the assessor visits. Red Tractor's combinable crops standards expect store hygiene records, and "we did clean it, honestly" is not a record.

The log has a second use: when something does go wrong mid-winter, the record of what was done and when is the starting point for working out why.

What skipping it actually costs

The clean-down costs a couple of days of labour and perhaps £100–£300 in consumables and servicing. Skipping it risks the other end of the scale: a fumigation runs to four figures, a rejected artic load of feed wheat is roughly £5,000 of grain plus haulage coming home, and an infestation found late can put a discount on everything in the shed. A buyer who finds live insects doesn't send a warning — they send the lorry back.

Put that way, the sweeping looks cheap.

Frequently Asked Questions

When should you clean a grain store before harvest?

As early as the store can be emptied — June is ideal for most UK farms. Cleaning early leaves time for repairs, lets residual treatments be applied well before grain arrives, and gives insect monitoring traps a few weeks to prove the store is actually clean before you fill it.

What should a grain store clean-down include?

Complete removal of all old grain and residues, then cleaning from top to bottom: roof steelwork and ledges, walls, all handling equipment inside and out, drying ducts, the floor, and the intake pit. Vacuuming beats sweeping because it removes dust rather than redistributing it. Any history of insects justifies a residual insecticide treatment on cleaned surfaces.

Do I need to record grain store cleaning for Red Tractor?

Yes — assurance schemes expect documented store hygiene: cleaning dates, who did the work, any products used with rates and operator details, plus bait point maps and check records. A dated log kept as you go takes minutes; reconstructing one before an inspection is harder and looks like what it is.

How do you keep birds and rats out of a grain store?

Proof the building while it's empty: netting over vents and openings, brush strips and seals on doors, and gaps at cladding bases or around service entries blocked. Back that up with mapped, tamper-resistant bait stations checked on a routine. Proofing is more effective than baiting — bait controls what gets in, proofing stops it getting in at all.