Better fungicide fit for wheat crop

Developments in RL Plus, the interactive version of the Recommended List, should soon allow growers to tell how much total fungicide individual wheat varieties might need to achieve a specific level of disease control.

That is the message from ADAS pathologist Bill Clark and HGCA’s variety expert Jim McVittie, who agree that varieties have improved hugely in terms of disease resistance.

Recent work suggests as much as 20/ha can be saved by choosing those with good septoria resistance.

RL Plus already allows growers to interrogate all HGCA trials data.

That means they can band varieties according to their disease ratings, and select those most suitable for the likely disease risk.

Mr Clark uses results from the first year of trials to illustrate the differences between septoria ratings.

“We have been working with Robigus, Einstein and Consort,” he says.

“Robigus has a 7 for septoria, Einstein a 5 and Consort a 4.”

The work showed that Einstein needed far less fungicide than Consort.

To get less than 10% septoria with a two-spray triazole programme, Consort needed a total of 1.25 litres/ha of epoxiconazole. In contrast, Einstein needed 0.4 litres.

But to improve the level of disease control to less than 5% of septoria meant using 1 litre on Einstein, but over 2 litres on Consort – not legally achievable in a two-spray programme.

“These results show the potential savings,” says Mr Clark.

The difference was more than 20/ha.

The figures come from just one year of trials, so should be treated with caution.

But his advice for 2006 is to ensure that all wheat crops receive enough fungicide.

“It’s particularly relevant for this season,” he warns.

“Most of the wheat is behaving like an early drilled crop, so it’s likely to be a high disease pressure year.

Growers should concentrate on the septoria resistance ratings of their varieties, and treat them accordingly.

That may mean using higher dose rates.”

He is concerned that most growers do not use enough fungicide across a three-spray programme.

“You have to remember the background.

There is widespread septoria resistance to strobilurins and a continued drift in triazole performance.

“That means there is justification to increase the fungicide dose, especially on varieties prone to disease.

However, most growers have responded to lower grain prices by capping their fungicide use, which could be a big mistake.”

A look at national wheat yields suggests he is right.

While new varieties are responsible for adding 1% to yield each year, farm performance is not increasing.

Furthermore, septoria control levels are slipping, especially on varieties with low disease ratings, such as Consort.

HGCA-funded work on appropriate fungicide dose shows that the optimum fungicide input does not alter much, regardless of grain price.

“There’s a danger that you won’t get the best from your wheat if you don’t exploit its ability to respond to fungicides,” he warns.

“Growers are right to spend less on resistant varieties, but they must take a look at how much they are applying.

This is particularly important with triazoles, whose activity has declined again this year.”

All the newer varieties show a very good yield response to fungicide use, notes Mr McVittie.

“Most of them give more than 2t/ha. So if you can’t afford to apply the required amount, you should be growing varieties with the highest septoria ratings.”

He believes growers won’t be successful with varieties with a rating of four for septoria.

“We don’t yet know what value a disease resistance point has, but work has started to try to determine a figure.

When we have this type of information, it will be included in the Recommended Lists.”

“Wheat varieties are getting much better,” stresses Mr Clark.

“Standards have risen considerably and growers need to concentrate on how to manage these improved varieties.

If they get it right, there’s scope to spend less.”