Strobs applied at robust rate

15 March 2002

Higher fungicide doses can lift yield and quality

By Brian Lovelidge

MANY cereal growers have the wrong mind-set about fungicide doses, according to Masstock agronomist Richard Cull

He says they are so focussed on using the lowest possible rates that they lose sight of the significant yield and quality benefits of higher doses, particularly of strobilurins.

"Growers find it so easy to put half a can of strobilurin less in the spray tank to save £12/ha, but ignore the fact it could have earned them an extra £35-50/ha.

"Yet when advised to halve their normal seed rate for early drilled wheat, saving £20/ha or more, they often dont want to know.

"Growers usually say they want the most profitable crop, rather than the cheapest. But when you tell them it will mean spending £10-12/ha more on a strobilurin they usually change their minds, even though their decision will probably restrict yield potential and profitability."

The pre-occupation with cutting fungicides and other inputs to the bone has often been prompted by arable consultants employed to produce crops more cheaply, claims Mr Cull.

"Thats the wrong approach. They should aim to produce crops more profitably." That often means using higher rates of strobilurins so crops benefit fully from their physiological yield boosting properties.

This seasons unprecedented amount of September-sown cereals – an estimated half the total in his area – means higher fungicide rates may be imperative, particularly for farms which failed to reduce seed rates.

Excessively thick crops will require skilful manipulation and PGR treatment to prevent lodging, says Mr Cull, who is now based in the south-west but previously spent 11 years working in East Anglia.

"Heavy disease pressure, notably from septoria and rhynchosporium, is the norm in the south-west, so high fungicide rates are needed every year. Whats right for Norfolk and Suffolk isnt always appropriate for the south-west, but I think more robust rates would also pay in other areas."

On septoria-susceptible varieties like Tanker, Mr Cull usually recommends 0.75 litres/ha of Mantra (kresoxim-methyl + epoxiconazole + fenpropimorph) for T1 and T2 sprays and 0.5 litres/ha for more resistant types like Claire and Deben at T1.

This season, he will be adopting the same stance with new strobilurin Opera (pyraclostrobin + epoxiconazole).

High disease pressure, with septoria already well established, may well merit dose increases, believes Peter Watts (left). Richard Cull (right) says concentrating too hard on dose cuts can be false economy.

&#8226 Low rates restrict potential.

&#8226 Thick crops need robust approach.

&#8226 Heavy disease pressure in south-west.

&#8226 Farm plan to stay flexible.

Strobs applied at robust rate

FARM manager Peter Watts is reluctant to jeopardise output on his Devon unit by over-cutting strobilurin doses. "To get a significant strob yield boost, it must be applied at a robust rate and in good time.

"You dont get such a good physiological benefit using low rates. I reckon we get a 10% yield increase from this effect, with our first wheats doing around 4t/acre."

Mr Watts farms about 500ha (1235 acres) at Lyneham Estate, Yealmpton, Plymouth, of which 400ha (988 acres) is arable.

He grows Claire, Deben, Tanker and Eclipse winter wheat, Fanfare and Leonie winter barley, Jalna and Aintree winter oats and has 40ha (99 acres) of Victor spring beans.

Winter cereal drilling started on Sept 4 and finished on Oct 9, about the time he normally began until five years ago.

By January, the earliest crops were well tillered, with the biggest plants having 15 tillers or more and "massive root systems".

Mr Watts crops are not excessively thick, however, thanks to reduced seed rates, which ranged from 75kg/ha (0.6cwt/acre) for the earliest drillings to 112kg/ha (0.9cwt/acre) for the latest. Five years ago, 170-180kg/ha (1.3-1.4cwt/acre) was the norm.

Varieties like Claire and Deben with septoria resistance ratings of 7, his T1 spray – usually applied with Meteor growth regulator at GS30-31 – comprises 0.5 litres/ha of Mantra or 1 litre/ha of Twist (trifloxystrobin) plus 0.5 litres/ha of Epic (epoxiconazole).

"We get high disease (and aphid) pressure in Devon, but well have to wait to see whether we need to push up fungicide rates," says Mr Watts, who has long used strobilurins .

All chemicals are bought on the open market and on the advice of independent agronomist Don Burridge, who has visited the farm for 20 years. This year, Opera will probably be tried on some of the acreage. &#42

Septoria and mildew lurking in Claire winter wheat make low doses a risky strategy.

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