What to do to combat Kzeae

19 March 1999

Giving best start in life

By Jessica Buss

PREPARE maize ground for drilling in spring with just one pass of cultivation equipment to get the crop off to a quick start and minimise compaction.

Gordon Spoor, Silsoe College, Beds, warns that any check in maize growth is serious, and the crops success depends on a good seed-bed.

When preparing a seed-bed avoid soil moisture loss, capping, compaction and poor drainage.

"Moisture loss is caused by excessive cultivation, capping occurs when the surface is too fine, and compaction is entirely from wheel traffic. Drainage is poor when there is a fine tilth over a coarse one," says Prof Spoor.

He says his ideal method for cultivating a maize field is to plough, or use deep tines, follow with a press and then power harrow once before drilling.

Most growers plough, either in autumn or spring, and when that ploughing is of poor quality it is difficult and costly to repair. Furrows should be tightly packed with a level surface and no cavities, he says.

Where fields have been autumn ploughed this can allow direct drilling, requiring no more than one spring operation even on difficult soils, he advises. But deep working can remove moisture from soils and brings up unwanted clods, he warns.

When direct drilling, he recommends avoiding excess penetration by setting discs carefully, using specialist machinery and not setting spring tines too deep.

On light soils that are ploughed in spring it should be possible to use a plough press and then drill. "But on heavier soils you may need to work deeper after the plough, but with good depth control to avoid going too far down," says Prof Spoor.

Even though you cover wheelings they are still there, he says. Reducing the number of passes by combining operations will help cut wheelings and, therefore, compaction.

Power harrowing after ploughing can create a good seed-bed. But the first pass into undisturbed plough furrows does most good; a second pass is less effective and may increase compaction.

"Adjust forward speed to get as close to a perfect seed-bed as possible in that first pass," he advises.

Wheelings made on each pass are influenced by tyre pressure, which can often be reduced to half the normal rate to cut compaction. Pressure on the ground is never less than the tyre inflation and will depend on the tyres ply rating.

"Always operate at the lowest possible tyre pressure, but never too low for safety reasons."

Prof Spoor suggests a gauge should be used to check tyre pressures are appropriate for each operation. That includes checking front tyre pressures which can also cause compaction. Alternatively, buy small, low pressure tyres, which are inexpensive.

Avoid making a fine seed-bed over coarser material which will not drain well and can become waterlogged in wet weather. Also be aware that discs will create a pan at working depth after a number of passes, warns Prof Spoor.


&#8226 Neat ploughing.

&#8226 One subsequent pass.

&#8226 Lower tyre pressures.

Fingers crossed…

MANY maize growers will be crossing fingers and hoping that sunny weather this summer means a K zeae-free year.

Kent grower and dairy producer Jeremy Wilson who grows 28ha (69 acres) in the Elham Valley suffered last harvest when his maize crop was badly hit by K zeae and poor weather prevented quick harvesting.

But to compound worries, wet weather has caused problems since harvest. "Its been wet all winter so we have recently resorted to having a contractor plough our land with a bigger tractor."

This means Mr Wilson has not been able to follow NIAB advice to plough stubbles in autumn to ensure all infected material is buried. However, he is not convinced about whether cultivations would remove the threat.

"We followed all these guidelines last year and still managed to contract the disease."

Potential for growing other crops such as wheat for whole-crop was also lost by atrocious weather last autumn. "And growing spring whole-crop is not an option because the yield is too low.

"But Im going ahead with maize, despite a potentially a bad start because of the weather. So we will wait with trepidation and hope the weather remains good during the critical period for K zeae infection."

Trials for best control

A SERIES of trials will be conducted on maize sites this year by the MGA in an effort to find out more about fungicide control of K zeae.

MGA director of operations John Morgan says it is concerned about the amount of K zeae found on farms last year. "It could be a problem again because we know so little about the disease and which fungicides control it.

"It caught us on the hop last year so this year, we will be seeking Pesticide Safety Directorate approval for fungicide control.

"We will also be running sessions on what to look for in maize and advise growers to check their crops carefully so they can spot it early. When its found it can be harvested rapidly and at least half the crop can be saved," says Mr Morgan.

What to do to combat Kzeae

A number of steps can be

taken to tackle the new

maize disease K zeae.

James Garner reports

ERADICATING K zeae, a disease which struck UK crops for the first time last year, will not be easy with bad weather affecting control options.

Advice to spread slurry and plough in debris was hampered by wet weather at harvest.

And NIABs head of herbage and fodder crops Jim McVittie says there is little good news for maize growers who want to prevent K zeae infection this year. "Some things have gone in favour of the disease.

"Wet weather stopped growers ploughing debris in during autumn. But it also meant any opportunity to sow another crop, such as winter wheat for whole-crop was lost."

But Dr McVittie does add that theres every chance there might not be a K zeae attack this year.

"Crops in other parts of the world have been infected with the disease but it has been sporadic and inconsistent. One year its been there and has disappeared the following year."

Growers looking for safe options rather than risking another bout of K zeae this year have some hard choices to make. "It might be possible to grow some whole-crop spring wheat or a barley/pea arable silage but these must be drilled by late March."

Where ground conditions delay sowing wholecrop, consider kale and turnips as alternative crops, suggests Dr McVittie. Another alternative would be drilling Italian ryegrass in mid-April. "This gives a good yield in its first summer and mixing with hybrid grass varieties would result in a good two year ley."

Producers are also advised to consider using two to three different maize varieties to spread the risk. "Their slightly different maturing times might not coincide with conditions for K zeae to take hold," he says.

Moving to an early variety might reduce problems at harvest because theres a higher chance of getting the crop off the field in good weather conditions, cutting risk of infection.

Dr McVittie says that growers shouldnt be surprised to see maize facing a higher disease challenge. "It is more widely grown in the UK and the weather is warmer, meaning we are seeing increasing occurrence of disease."

However, he says that NIAB is trying to find some answers to K zeae, but needs at least another growing season to progress plans.

"We shall be looking at varieties and whether some show more resistance than others. There were varietal differences last year but its not known whether this is due to varieties showing susceptibility to the disease or whether certain varieties were at the right growth stage to be infected by the fungus."

NIAB will also be seeking off-label approval for fungicide use, but data needs to be submitted to the Pesticide Safety Directorate before recommendations can be given to producers.

Despite hopes of fungicide approval for next years maize harvest, there are practical problems to overcome with spray application. Its difficult to spray maize in September when the crop is almost fully grown, about 1.75m (6ft) tall and at most risk from K zeae, says Dr McVittie.

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