7 September 2001

Go for untreated farm-saved seed & pocket £15/ha

Sowing untreated seed

could save cereal growers

£15/ha this autumn.

Charles Abel finds out

how to do the job properly

to minimise risks to the

growing crop

EXTREMELY low disease levels on cereal seed mean sowing farm-saved seed without a fungicidal seed treatment looks more attractive than ever this autumn.

Growers could almost halve seed costs, slashing their outlay from £215/t for certified seed with a single-purpose fungicidal seed treatment to just £115/t untreated.

It is all made possible by the exceptionally low levels of Microdochium nivale, the fusarium species that causes seedling blight (Arable, Aug 31). That is the key target for single purpose autumn seed treatments, which typically cost £45/t.

Central Science Laboratory tests on 450 samples from across the country in July found no M nivale infection and National Institute for Agricultural Botany lab test results for harvested grain confirm the trend.

"Levels are very low," says Beds-based ADAS consultant David Parish. He has had results back for nine wheats drilled in October or November that have undergone tests at NIAB this season. Seven had no M nivale and none exceeded 1% infection.

His rule of thumb threshold for using a seed treatment is 15% M nivale infection. Anything below 5% is highly unlikely to need treatment. Mr Parishs figures are based on years of experience plus a major Home Grown Cereals Authority-funded project a few years ago.

"Between 5% and 15% infection is a grey area. Seed-bed quality, date of drilling and weather conditions will all have a part to play. For a late-drilled crop you would be looking to stay at the lower end of the scale, but for early September with a moist seed-bed 10% will be alright."

But growers must test seed first. "Disease levels will vary between regions and according to the weather at flowering in June, which affects the level of M nivale on the seed. It would be irresponsible to sow without getting a test done first," says Mr Parish.

Testing for M nivale costs £49/sample, with results back from NIAB lab test at Cambridge in five working days. "They are currently turning them round in three days," says Mr Parish.

Correct sampling is important. "You need to take several sub-samples from the grain you are planning to use as seed."

Parent crops should also have been managed for home-saving. "It needs to be planned from the outset really, with attention to crop management and separate storage, rather than simply dipping into the grain heap."

With test results to hand, a decision can be made on treatment. If none is required and seed is weed free and of a good grain size, there may be no need for a mobile dresser to put it over a gravity separation table. "That adds a further £25/t saving to the £45/t already saved on seed treatment," says Mr Parish.

However, getting unbagged seed into the drill may present logistical problems and if seed needs putting over a gravity separator a mobile dresser may still be needed. Royalty is payable at a rate of £5.55/ha if a processor is not used.

Bunt must also be considered. "It can wipe out the crop, so needs remembering. But if farm-saved seed has been grown from treated seed the risk is negligible. It just does not multiply that quickly in one season."

Soil-borne bunt is a potential threat, but only if bunt has been present locally and dry soil conditions have favoured its survival from harvest to sowing. "The risk this autumn is very, very small."

Soil-borne fusarium is dismissed as a red herring. "It is a different species from M nivale, which will not affect establishment," says Mr Parish.

"If seed is disease free, or below the treatment threshold, there really is no requirement for a seed treatment."

&#8226 Similar savings can be had in barley. Like bunt in wheat loose smut is only worth testing for if untreated seed was used to grow the farm-saved crop or if infections have been found locally. Leaf stripe, like M nivale, needs testing for, with a lower treatment threshold of 1-2%. "The yield impact is more direct than with M nivale in wheat," says Mr Parish. NIAB Labtest results for his clients are currently below 0.5%.

UNTREATEDFSS

&#8226 Very little Microdochium nivale = very low risk of fusarium seedling blight.

&#8226 £100/t saving possible.

&#8226 £17/ha total seed cost.

&#8226 Get seed tested first.

&#8226 Increasingly popular.