Archive Article: 1997/08/02

2 August 1997




HARVEST results will reveal whether the most expensive fungicide programme used in ADAS Rosemaund wheat trials produces the 0.5t/ha needed to cover the extra cost over the cheapest top performers.

Visually, and in assessments of septoria control, there is little to choose between £95/ha (£38.50/acre) and £55/ha (£22/acre) two-spray programmes on Riband. The most expensive cocktail was BASFs Ensign (kresoxim-methyl + fenpropimorph) at the full 0.7 litres/ha rate, plus 0.5 litres/ha Opus (epoxiconazole) at GS32/33 (May 2) followed by half-rate Ensign and 0.5 litres/ha Opus at GS39 (May 23).

For £55/ha, Dr David Jones, of ADAS Rosemaund, obtained apparently equal disease control with 0.5 litres Opus plus 1 litre/ha Bravo (chlorothalonil) followed by 0.75 litres/ha Opus and 1 litre/ha Bravo.

"At todays projected wheat prices, you need more than half-a-tonne of additional yield to justify moving up," says Dr Jones. The same Opus plus Bravo programme was the most profitable in Rosemaunds 1996 trials but he acknowledged there may be some extra maintenance of green leaf in the Ensign plot which will boost yield.

Last years work on fungicide doses for HGCA also highlighted the importance of application timing as dose rates are reduced, and that higher – but not necessarily full rates – can be more profitable due to better yield response than cheaper programmes giving apparently similar disease control.

With a full rate, says Dr Jones, application within a week either side of the optimum date may have little effect on disease control and yield but, with a reduced rate, this may only be a few days. This reduced activity is most pronounced with yellow rust but is also seen with septoria tritici.

Greater disease pressure this year shows up the poorer performance of mixtures which reduce the rate of Opus too much – as low as 0.25 litres/ha – and highlights the advantages of adding Bravo.

Dr Jones points out that while BASF has gone immediately down the formulation route with its strobilurin – kresoxim-methyl – Zeneca has made azoxystrobin available on its own as Amistar. However, he feels its protectant activity needs the addition of a triazole partner to eradicate any disease present when the spray application is made.

"I see the strobilurins as being very much ideal partners for triazole fungicides because the triazoles will affect disease which is already starting to develop while the new chemicals give long-lasting protection against further infection," says Dr Jones.

"I would use Amistar at GS31 plus a triazole which neednt be the best triazole, but should be strong enough for early eradicant activity."

However, for the best performance with the strobilurins he favoured an early application combined with a powerful triazole such as Opus, followed by 0.5 litres/ha Opus on its own at GS39. On current pricing this might work out at about £75/ha (£30/acre) but prices for next season could easily change because of market competition to favour alternatives which are currently more expensive.

With wheat valued at £80/t or less, and a number of new products coming into UK market, there is likely to be downward pressure on prices as the old and new materials jockey for market share.

REGIONAL REACTION

1. SCOTLAND

IT IS important for growers to realise each strobilurin has a different spectrum of control, and that many of the new fungicides are good protectants, but wont deal with pre-existing disease, says Simon Oxley of the Scottish Agricultural College.

Quinoxyfen (Fortress) is a good protectant against mildew but not an eradicant like the morpholines to which farmers are used to, he points out. On barley, a mixture of Fortress for mildew control and Amistar against net blotch could be a good option.

"My main worry about strobilurins is that people treat them like triazoles or put them on too late while cutting the rate too much," he adds.

2. SUSSEX

FUSARIUM, Septoria nodorum, mildew and sooty moulds all flourished in southern cereal crops during June. "Amistar controls the range of diseases that are appearing this month, and it will prolong the green leaf area and delay natural senescence," says Zeneca technical manager, Chris Ursell.

David Andrews, of Chichester-based distributor Bartholomews, has Amistar in company trials. He is an advocate of prophylactic spraying at the critical timings although he acknowledges that ear wash sprays pay in only two out of five years.

"This season we are sure ear treatments will be cost-effective. MBC-based products have not worked for a number of years, probably due to resistance, so we are recommending specific ear spray triazoles such as Plover and Folicur."

3. CAMBRIDGESHIRE

&#42 L HUTCHINSON deliberately piled the pressure on to new chemistry at its demonstration site at Walsoken near its Wisbech headquarters.

All products were applied at third node stage, which would not have shown any to their full advantage, but provided a benchmark at least.

Farming below sea level, frequent early morning mists and heavy dews keep diseases ticking over when the rest of the country is drying out and also contributes to high levels of mildew. Company agronomist Andrew McShane picks out Fortress in particular as giving long lasting protection against this disease and "tremendous" responses even at half rate.

While not specifically positioned as a mildewicide, Amistar showed good activity against the disease on the barleys Fanfare, Regina and Rifle, he adds.

Against Zenecas guidance, Amistar had been applied without a triazole partner. Even without any anticipated yield effect, Mr McShane describes it as a tremendous product for its fungicidal activity alone.

BASF maintains that Ensign, the second strobilurin, should have been applied earlier. But, nevertheless, held yellow rust well given the pressure level and, for a single full dose, had also done a good job against septoria tritici in Consort.

Looking forward a few years, Cyanamids metconazole promised to prove a "cracking" triazole in the epoxiconazole league. It had done an "excellent" job against yellow rust in Brigadier considering the disease pressure and also against septoria tritici and generally had kept barley clean. Mr McShanes verdict – "a good all-round top quality triazole, though we wont see any real revolutions in triazole chemistry now."

Tetraconazole from Monsanto looked a good all rounder but was no better than the current standards and might struggle to find a place in the UK. But he is quite impressed with AgrEvos fluquinconazole which had held off yellow rust. Novartis SAR (Systemic Activated Resistance), though supposed only to boost mildew resistance, had also some effect against rust.

Unix (cyprodinil) from Novartis, was a good product for mildew and stem base disease control, with some septoria nodorum activity. It was also a good barley product.

However, it had a weakness against yellow rust. With the acquisition of cyproconazole from the Sandoz stable, strategies combining the two products could be anticipated.

Mr McShane also subscribes to the view that a degree of common sense might be injected into pricing over the next 12 months.

Meanwhile reducing inputs might be a false economy, as the end result might be a poor sample, not even worth £80/t, and difficult to sell.

4. HUMBERSIDE

DONT think of new chemistry simply as good fungicides but as yield enhancers to get the best potential from your crops.

And Craig Morgan, technical manager with Profarma, adds that the best results will come from crops on poorer, light land or grown in stressed conditions.

On the unstressed silty loam at the CWS Goole estate where Profarma has its northern trials, he does not expect either straight strobilurins or mixtures to demonstrate their full capabilities. After all, untreated Brigadier has yielded 12t/ha (4.86t/acre) on the site, he points out.

"Where the new chemistry will score over the triazoles is on less retentive moisture sites," adds Mr Morgan. He favours selecting for these sites, varieties which are inherently likely to retain green leaf tissue longer than others. "These are the likely candidates on which to use strobilurin materials. Because of the poorer soils there may be more to gain, than for growers on better soils."

Earlier Profarma work has identified Encore, Drake and Rialto as wheat varieties that retain their green leaf area longer. CWS Agriculture has picked up on the trials and is planning to drill a large acreage of Encore this year in drought-prone fields at its Cheshire estate.

Mr Morgan warns growers and consultants against trying to fit reduced rates of strobilurins into fixed budget fungicide programmes just for the sake of it. His Yorkshire trials show that green leaf area is retained provided a full unit of strobilurin is used – although it can be split – but disease control suffers when the total dose is reduced.

How do new generation fungicides stack up against familiar mixtures? We seek economic, and technical, advice across the country.


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