Strob arguments prompt large dose of scepticism

2 April 1999

Strob arguments prompt large dose of scepticism

Manufacturers strobilurin

advice has been greeted with

some scepticism on Farmers

Weeklys barometer farm in

Lincs. Andrew Blake reports

STROBILURIN fungicide has already been applied to winter wheat this spring at Elms Farm, Caythorpe, where Tony Wright remains unconvinced by manufacturers arguments about managing disease resistance.

Contrary to FRAC guidelines (Arable Mar 19), he and Aubourn Farming agronomist Bridget Caroll intend to adopt a repeat low-dose programme, admittedly in mixtures with triazoles later on, to keep on top of disease from the outset.

"If you start with no disease competition it is a different picture to trying to cure something once you have it," explains Mr Wright.

After a wet spell in the first two weeks of March, the weather came good allowing fieldwork backlogs to be cleared. "For the next two weeks we had only two days with rain. But we still have plenty of moisture below which should be helpful especially on our heathland."

Besides sugar beet drilling, which finished on Mar 25, operations included applying the first routine split dose of 1 litre/ha of chlormequat to the wheats at late tillering.

This years varieties are 8ha (20 acres) of Malacca for milling and 70ha (173 acres) of Riband and Consort for feed. "The Malacca is a bit of a departure for us," says Mr Wright. As a potential breadmaker and sown on Sept 15, it clearly merits a robust growth regulator programme. But, despite being sown slightly later than normal, so do the feeds, he maintains.

"We were a bit delayed by rain last autumn, which may be a blessing in disguise for second wheats on the heavier land. But everything was in by the end of October." That is particularly important on the heathland to counter the risk of summer drought.

With the temperature above 10C (50F) a small saving on Li700 regulator adjuvant was available. "I am sure it helps uptake in the cold, below 8C. But we did not need it this year."

With grain prices as they are every saving helps, he stresses. "We have got to be aware that cereal margins are going to be extremely tight." That is mainly why he cannot accept FRAC advice on strobilurin dose rates. "We are aiming to spend a total of £37/ha on fungicides. It was £46/ha last year. Some merchants are proposing programmes that will run to £74-99/ha. That could be most of the profit in a lot of cases. I certainly do not think that can be justified unless you have land which does 5t/acre consistently."

The repeat low dose approach involved an initial 0.15 litres/ha of Landmark (kresoxim-methyl + epoxiconazole) along with the chlormequat and some manganese and magnesium to all the wheats. At 18-20 days intervals it will mean four sprays up to and including flag leaf.

Last season the farm used Amistar (azoxystrobin), Landmark and Mantra (kresoxim-methyl + epoxiconazole + fenpropimorph) at a range of timings to good effect. "But we shall probably stick to Landmark this year with the addition of some extra epoxiconazole or tebuconazole if needed as it looks like being the most cost-effective. I am told Amistar is likely to be in fairly short supply."

Mr Wright believes disease resistance worries about strobilurins are being over-played. To date the only disease to develop it is mildew, and only in Germany, he notes.

"We have used low dose strategies with other fungicides for a long time with good results. Besides mildew isnt a great problem for us on most varieties. I suspect the Germans may have more susceptible varieties."


&#8226 FRAC guidelines shunned.

&#8226 Low dose repeat sprays plan.

&#8226 Eyespot of little concern.

&#8226 New beet tramlining method.

Barometer round-up

&#8226 WEST – Andrew Cooke says manufacturers previous marketing activities make it difficult to accept FRAC advice. Producing the same active ingredient at the same concentration under various trade names is one example of confusion caused, he says. Strobilurins will definitely figure at North Farm this year. "But all I can say is they are unlikely to be used at the makers rates."

&#8226 SOUTH-WEST – Paul Dale can see the logic behind the FRAC message. It is akin to that about low doses of antibiotics on animals encouraging bacterial resistance, he says. "But there again is it a case of manufacturers talking their trade up when farmers are looking to reduce costs?" Problems in Germany may not be comparable, and without more independent UK research he remains wary but will act on agronomist James Stuarts advice at Restronguet Farm.

&#8226 EAST – Robert Salmon says practice at Hyde Hall, which rarely involves spraying before GS32 (second node), is not far from the FRAC guidelines. "It is wrong to go for a repeat low dose because that will select for resistance. But as long as you use a three-quarter dose at least once in the programme that should be OK. We cant afford two heavy doses."

&#8226 SOUTH – "The German experience is worrying," says John Chalcraft. "We had tremendous success with Landmark and Amistar on a late drilled crop last year. It is still only year two of full-scale field trials and we have got to be careful to protect them." Application at New Farm this season, under agronomist Tom Blanchards advice, will probably be close to that advocated by FRAC.

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