27 March 1998

Which one is first… pgr, fungicide or nitrogen?

Winter barley managementcomes under the scrutiny ofour barometer farm seriesthis week, posing particularchallenges for our south-western barometer farm.Andrew Blake reports

BIG differences in growth stages and disease pressures in Stewart Hayllors Hanna and Muscat winter barley at Gullaford Farm, Landscove, Devon mean inputs are being juggled carefully.

Main dilemma is deciding which operation gets priority – applying nitrogen or controlling net blotch, checking brown rust and getting growth regulator on. Individual fields, all for feed, clearly need different approaches.

Most had about 63kg/ha (50 units/acre) of N in two splits last month. And with the 9ha (23 acres) of very forward Muscat already at first node (GS31), there is some urgency for a top up to take the total to 188kg/ha (150 units/acre).

"Once it is moving we must keep it going to maintain the tillers," explains Mr Hayllor. "We dont want it to run out of N."

Mildew is rarely a problem and easily controlled when it appears, says ADAS adviser Bill Butler. "But we cant afford to let net blotch or rhynchosporium take hold."

Net blotch in Muscat is already obvious and rhynchosporium could take off if the weather stays warm. Early-sown Hanna approaching stem extension (GS30) is smothered with brown rust on the older leaves. "I have not seen it as bad as this for years," says Mr Butler. By contrast a much thinneradjacent field sown two week later is almost disease-free, he notes.

In the Muscat there is little doubt that the first fungicide must precede the fertiliser, says Mr Hayllor. A pressing need to insert a straw strengthening 2 litres/ha of 3C Cycocel (chlormequat) regulator, adds to his argument.

Local trials and recent ADAS Rosemaund work suggest there is little mileage in adopting any of the newer regulators for barley, notes Mr Butler.

Amistar order slashed

For the fungicide he had hoped to try some Amistar (azoxystrobin). "It is very good on net blotch." But his group buying order for 8000 litres has been trimmed to just 200 litres.

Depending on price the first hit would have been 0.5 litres/ha of Opus (epoxiconazole) with 0.6 litres/ha of Amistar, with the aim of saving on the second awns-emerged spray. All dose rates are based on university of life experience, he says.

"But we shall probably have to stick with what we used last year when we majored on Opus." He admits flusilazole has its enthusiasts, but bases his decision on local trials and wider HGCA work. "Opus is as good as anything for rhynchosporium and net blotch."

The reduced rate approach of 0.5 litres/ha tank-mixed with 0.3 litres/ha of Corbel (fenpropimorph) to enhance rhynchosporium control, followed by another 0.5 litres/ha as second spray, has failed only once in the past – on Pipkin, notes Mr Hayllor.

Much of the farm, with its annual 1120mm (44in) rainfall, lies in a natural amphitheatre. "It is the worst I see for rhynchosporium," says Mr Butler.

Brown rust in the Hanna this early has created another poser. Although confined mainly to the lower leaves, it is clearly a threat if the weather stays warm.

"It is an explosive disease which can spread very quickly." The same mix would easily control it. But treating so soon would mean having to spray again within a month to be sure of containing net blotch and rhynchosporium, he explains.

So they have plumped for a compromise 0.25 litres/ha of just Opus applied now, just to keep the rust in check. "It shouldnt cost more than £3/acre," says Mr Butler.

"It is another operation, but I think we do need to do it. It will buy time," says Mr Hayllor.

Getting to grips with barley disease – Landscove farmer Stewart Hayllor (right) and ADAS adviser Bill Butler plan their first fungicide spray.

Rampant net blotch (left) and brown rust in south-western barleys need urgent action. Elsewhere the disease pressure is less intense.

BAROMETER ROUND-UP

&#8226 East: David Pettitt is relaxed about his 32ha (80 acres) of Regina for malting, which was due for its first fungicide/growth regulator this week. Its full 112kg/ha (90 units/acre) of N was on by Feb 25. "There is not a great deal of disease on it. "We are sticking with 0.1 litres/ha of Opus with 0.25 litres/ha of Corbel. Mildew is the main worry. We will perhaps try some of the new chemistry like Amistar as the second spray, but it is said to be very tight. I just wonder whether supplies are being held back to keep the price up."

&#8226 Midlands: For Steven McKendrick growth regulation rather than disease control is the priority after about a third of the total N went on last week. There is net blotch in Fighter but not at worrying levels. "The Pastoral has the odd fleck of rhynchosporium, but the mildew is old mildew. We are pretty much where we want to be." 1.75 litres/ha of 3C Cycocel used relatively early is his preferred first regulator. "Using it sooner helps reduce bounce-back and the need for Terpal later."

&#8226 N Ireland: Michael Kane is in no hurry to spray his Regina and Jewel, although he is glad to have got the first nitrogen/ sulphur dressing on last week. Sulphur trials a few years back proved inconclusive, he notes. "But going by HGCA work sulphur is probably an advantage on our light soils considering where we are geographically." Mildew was encouraged by warm weather a month ago. "But it has dropped off since. We shall go with our first fungicide once the fertiliser catches. It will probably be half rate Punch C as it is better on rhynco than Opus and maybe more economical."