3 July 1998

How no-chem control can keep those bugs at bay

Grain storage must improve

– markets demand it and

assurance schemes reflect

those demands. In this

special feature we consider

the key issues, starting here

with reports on pesticide

resistant mites by

Andrew Blake and chemical

free storage by the CSLs

Ken Wildey. Edited by

Charles Abel

DURING intake and then in store, it is vital that grain moisture content and temperature are reduced to below threshold levels for insect and mite breeding.

The key figures for cereals are 14.5% moisture content and 10C (50F). But it is pointless striving for one threshold without the other.

The combination is important because moisture is critical for mite development and temperature for insect breeding. Oilseeds must be no more than 7% moisture to be safe from mites.

Drying grain is a familiar task. But for longer-term safe storage, cooling to at least 10C (50F)after drying is essential, and easily achievable. With the right equipment it is also very cheap.

Use a cooling system linked to a differential thermostat that will trigger cooling fans when the ambient temperature is only 4C (7F) less than that of the stored grain. HGCA-funded research confirms this provides rapid cooling even after a warm early harvest.

Target temperature should be 10C (50F) by November and there is no reason why it should not be down to 5C (41F) by Christmas. The cost should be no more than 10p/t, and half that if you have access to a night rate electricity tariff. Most farmers cool their grain but stop short of achieving really low, safer temperatures. Surely this is not because of the cost?

Store monitoring is arguably the most important part of the whole job, and generally the least well done. It should cover temperature, moisture and pests.

Permanent temperature probes can be set in the grain and linked to a central recorder. Probes also pinpoint localised heating, which can quickly be acted upon.

Regular store checks

If you use a hand-held probe, temperatures must be taken from a range of positions and depths. It is important to do this in a regular, repeatable pattern. This allows comparable records to be kept so trends can be spotted, and action taken to get back to that low, low, temperature target.

Although grain from the combine may have been dried to the safe target, the moisture content at the surface is likely to rise during storage and must be checked frequently with an accurate moisture meter. Any increase will encourage surface mites and moulds. If there are any signs of problems developing the grain may have to be turned and in some cases redried.

Monitoring grain pests has never been easier after UK development of the PC trap at CSL.

At about £3 each, the traps are a cheap and highly effective set of eyes working 24 hours a day, seven days a week. Set in the grain, both at the surface and just below (one trap/10-20t of grain) they will find any insects present much more effectively than a storekeeper using spearing and sieving.

lSuppliers: Igrox (01728-628424), Graincare (01206-862436). &#42

Low temperature, low humidity levels and pest checking can ensure no-chem grain.