21 May 1999

Increase in soil-borne mosaic virus sightings

By Charles Abel

SOIL-borne mosaic virus (Arable May 14) spotted in two fields of Equinox on a Wilts farm has been confirmed in three more fields on the same farm. The infection is believed to be several years old.

Equinox, Savannah and Consort are stunted and infection is considered severe. Yield losses could be up to 70% in affected patches, the CSL confirms.

So far no outbreaks have been found on adjacent farms. "Fortunately the farm, which wants to remain anonymous, is a very self-contained unit," says CSL scientist Neil Giltrap.

Whether the infected crops can be harvested has yet to be finalised. "The cropping is not very high risk in terms of spreading infection. It should be fairly easy to keep it contained."

The farm is now under a provisional statutory hygiene notice, requiring all machinery leaving the outbreak fields or farm to be washed down and disinfected. Personal footwear must also be disinfected.

But the disease may already be present elsewhere. The size of the infected areas and their spread across the farm suggest initial infection occurred some years ago, notes Dr Giltrap.

All wheat on the farm and any neighbouring land where the farms machinery was used is now being surveyed by the Plant Health and Seeds Inspectorate. No further outbreaks have been found so far.

Tests suggest the outbreak strain is similar to those in France. But CSL virologist Christine Henry refutes suggestions that limited testing facilities could let samples infected by other strains slip through the survey. "We start off with a very broad test and then refine it if we get a positive result."

How the disease arrived on the farm remains unclear. Possible infection sources include soil associated with seed potatoes, nursery stock, transplants, root vegetables or even cereal seed.

"The best way to control this disease is to avoid it," says Dr Giltrap. Contractor hygiene and avoiding soil movement between farms is most important. Growers should also note that there are no EU standards for the disease on imported produce, he warns.

&#8226 HGCA-funded testing of UK wheat varieties will start on infected sites in France and Italy this autumn, adds Ms Henry. "France and Italy rely on resistant varieties to continue growing wheat on infected sites, so it is worth testing for." Charger and Cadenza have shown good resistance. &#42

Oilseed rapes future lies in wide rows?

GROWING oilseed rape in wider rows could be just one of the management tweaks the crop needs to reinforce its margins after CAP reform was one of the messages at a Masstock/Cargill/Cyanamid farmers meeting in Wantage, Oxon, last week.

On most arable farms oilseed rape will continue to be the most profitable break after Agenda 2000, according to Masstocks James More. "It is a very good entry for first wheats, and spreads machinery and labour peaks. And, very importantly, it spreads marketing risks."

Putting a 3.5t/ha (1.4t/acre) harvest 2000 rape crop on a par with a 7.4t/ha (3t/acre) crop of wheat at £70/t, Mr More believes there is plenty of scope for improving margins. But to be profitable the crop requires good management. "It can be managed well and responds very well."

Lee Robinson, for Nickerson Seeds, noted that French growers have had good results from using 25cm (10in) rows, and UK trials with the companys new conventional variety Escort have found the practice has much to offer.

Advantages include better air flow through the crop and, therefore, less disease, thicker stems and so less lodging and easier harvesting. "It is easily achieved by blanking off the drill coulters," said Mr Robinson.

Concerns that crops sown this way are more susceptible to pigeons and rabbits are unfounded, he said. "We have found that if crops do get attacked, the plants are stronger so they tend to recover better than conventionally established ones."

On the "hot potato" of hybrid seed cost, CPB Twyfords Keith Best said the crop price would have to fall to £40/t before the extra yield no longer compensated for it. "But please do not try to grow hybrids if you are into broadcasting or use minimal cultivations where there is a lot of trash."

Cyanamids new fungicide, metconazole, expected to be available next year, has given similar disease control to Folicur (tebuconazole), but has had a stronger growth regulatory effect in trials, added Masstocks Tim Horton. "So it could give us the potential to push the crop even harder." &#42

Growers told not to panic

NEWS that wheat mosaic virus has been confirmed on a farm in Wilts should not panic growers, says Mike Carver of ARC.

"Currently it is confined to a very small area. And there is already a reasonable level of resistance to the virus in several UK wheat varieties."

Its arrival was totally expected, he continues. "Large areas of France and Italy have been infected for a while. In France, there are some areas where only resistant varieties can be grown."

Growers must realise that it is a soil-borne virus, so is likely to achieve a slow, methodical spread, Dr Carver says. "Take the same precautions as you would for barley mosaic virus if it is confirmed. Soil movement has to be minimised." &#42


&#8226 LEVY collections from horticultural producers to fund research should be raised to a minimum net sales threshold of £50,000 for the next five years the HDC has advised MAFF.

&#8226 DANISCO Seed and Dow AgroSciences have merged their oilseed rape breeding programme to develop improved lines for growers in Europe and North America. Advanced technology will be used to develop higher quality crops and hybrids, they say. In the UK the resulting varieties will be marketed by Danisco. &#42

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