peak levels

5 December 1997

Check now – pests at


peak levels

Grain store problems are rife this season. Amanda Dunn

and Edward Long report the latest developments from

Grain 97 and practical advice from storage experts

to help you avoid some of the commonest pitfalls

CHECK grain stores for pests and vermin now, growers are being urged. Insects, mites, rats and mice are all at their highest levels for years.

The cost of damage to cereal growers could exceed £50m, says pest control specialist Chris Stapleton of ArrestaPest, Great Gidding, Huntingdon.

"There are a lot of beetle problems and muggy weather is encouraging a build-up of mites. We are being run off our feet with calls."

The foreign grain beetle is more common than usual and saw tooth and red rust grain beetles are easily found. "We are also seeing a lot more mites than normal. They are starting to build-up on top of stored grain, encouraged by damp air."

Not only can such pests hit quality and marketable yield directly, they can also cause indirect losses when grain bulks heat up and trigger mould formation.

Mr Stapleton says the stop/go cereal harvest is to blame, forcing warm moist grain to be put in store. About half East Anglias stores are not monitored regularly so are now at risk from pest build-up, he warns.

Infestations can be controlled in most cases. But the store environment will be altered, encouraging moulds which discolour grain, upset germination and can cause chitting.

Pest specialist Henry Cobbald of Dealey & Associates, Sapiston, Bury St Edmunds, echoes such views. He believes the black clouds of fungal spores seen behind combines at harvest are also to blame.

"We are finding foreign grain beetles in almost every case we deal with. The pest is a fungus eater and has made the most of the mass of black spores which came in with the grain from the combines. It has bred very rapidly and created the conditions to encourage the more usual grain insect pests to breed."

Despite stores being treated properly, hot pre-harvest weather caused chemicals to degrade rapidly, leaving foreign grain beetles free to move inside from nearby debris, Mr Cobbald believes. The warm September then made it difficult to cool grain sufficiently to prevent breeding.

Although cereal prices are low, growers must treat stored grain, he says. Options for beetle control are either to move the grain and ad-mix an organophosphorus dust or spray, such as pirimiphos-methyl (Actellic and similar). Cost is below £1/t.

Alternatively a contractor could fumigate with phosgene. However, the gas is not very efficient against mites, he says.

Mites are best dealt with by raking an insecticide powder into the top of the grain bulk. But a build-up of resistance means that is now less effective and no other materials are approved for mite control.

Fumigation for an average farm costs £1-5/t and stores still need checking every two weeks after treatment, he advises. "A lot can go wrong very quickly."


&#8226 Highest levels in years.

&#8226 Stop/go harvest to blame.

&#8226 Foreign grain beetle and mites feeding on fungal spores.

&#8226 Check stores, treat if needed and keep checking for recurrence.

&#8226 Mites tricky to control.

Warm weather blamed for vermin plague

UK grain stores are suffering the worst invasion of rats and mice for at least a decade.

The warm summer and cold October are to blame, says Henry Cobbald of Suffolk-based Dealey & Associates. Good summer weather was ideal for breeding and the unusually cold, frosty October encouraged vermin into buildings sooner than normal.

"Mills are a lot more vigilant in searching for rat droppings than ever before," stresses Mr Cobbald. Even a single dropping in a load can lead to rejection. Smelly urine can have the same result. Rats are incontinent and urinate about 40 times for every dropping passed, he explains.

"Great care must be taken to ensure rats, and mice, are kept out of grain, otherwise the economic consequences could be grave."

Do-it-yourself baiting with a warfarin derivative can be effective, provided it is done regularly, he advises. If the job is put off or stopped as pest numbers seem to decline it can be far less effective.

See more