Archive Article: 1997/07/19

19 July 1997




New generation fungicides are already showing their mettle in French cereal trials with the leading research organisation ITCF. David Millar looks for lessons for UK growers.

CONFIRMATION of the effectiveness of new generation strobilurin and triazole fungicides is not hard to find in ITCF trials near Paris.

Growers, however, need to look carefully at the timing and sequences likely to give best overall disease control.

What isnt disputed is the major role in eyespot control taken in France by Novartis cyprodinil (Unix).

No other product in trials by Claude Maumené, of ITCF (Institut Technique de Cereales Fourrages), is expected to show the control achieved by cyprodinil in an early season role.

The choice of an eyespot product is particularly important in France where there is evidence of resistance to prochloraz in some strains of the fungus. Cyprodinil controls these resistant strains although there is another new codenamed product – 96B from BASF – which is performing as well as prochloraz in some situations. It combines the strobilurin kresoxim-methyl with epoxiconazole.

Mr Maumené is not keen on the manufacturers strategy of using this as a first GS31 spray in a two-spray programme because the dose required for eyespot control is 20% greater than that required to control septoria.

Control

"We dont expect as good control from 96B on eyespot as Unix," he says. "We would prefer to use it as a second spray, keeping Unix against eyespot as a first spray."

In his trial at ITCFs Boigneville headquarters, good overall disease control was obtained this year on wheat treated with 0.8kg Unix + 0.5 litre Alto at GS31, followed by 1 litre 96B at GS45.

Plots treated with the full rate of 1 litre 96B at GS31 and GS45 appeared to show heightened drought stress, according to Mr Maumené.

Adjoining trial plots treated with reduced rates of 96B down to 0.25 litre showed little difference in septoria control until well after ear emergence.

Another good result in overall control in the Boigneville demonstration came from a three-spray programme of the type favoured by many French growers concerned to get late ear disease control.

Based again on the Unix + Alto starter at GS31, Mr Maumené followed up with epoxiconazole (Opus) at either 0.8 or 0.5 litre at GS45. This time 0.75 litre of metconazole (Cyanamids Caramba) was applied at GS55.

In the absence of eyespot, a two-spray programme based on full rate Alto (1 litre/ha) at GS31 followed by Opus at GS45 is also used by many French growers.

Mr Maumené points out that Alto will not control septoria on leaves which havent emerged at the time of spraying. The combination is good but doesnt outrank the control from a GS31 spray timing with the new combination of Zenecas azoxystrobin (Amistar) followed by Opus from three to six weeks later.

"It seems azoxystrobin gives some flexibility for the timing of the second spray. It doesnt mean we are recommending people to wait six weeks for the second spray but it does mean they can get control if it rains and spraying is delayed," he says.

Results

Similar results have been seen in other trials although full yield and other data wont be available until after harvest. A combination using azoxystrobin with a triazole as a second spray is also being examined.

Other plots at Boigneville confirm azoxystrobins best performance as a preventive against septoria, says Mr Maumené. Treating at GS31-32 alone gave good results although some disease still showed on the flag and second leaves.

"That means we cant spray at GS31 and forget about it," he adds. Single sprays at either GS37 or GS45 also left the crop with septoria.

The French trials also compare single sprays at differing timings of new products from BASF (96B – kresoxim methyl + epoxiconazole) and AgrEvo (Vista CT – fluquinconazole + chlorothalonil).

Both gave best septoria control from GS37 sprays rather than the earlier GS31 timing which failed to protect the final leaves.

Mr Maumené points out that BASFs French marketing strategy for 96B as a first spray, is not mirrored by the trial which produces best results from its use on the flag leaf.

Although he has seen evidence of a greening effect from the strobilurins, he says it is difficult to see this producing extra money for growers.

A further septoria product – famoxate from Du Pont – is probably two years away from registration for the French market but does not stand out in the current season.

In the ITCF comparisons, it appears to perform better as a first spray when used in combination with Opus rather than the reverse programme.

Using the highly susceptible, trials-only variety Salmon, Mr Maumené has compared new and existing products for mildew control in wheat.

Best disease control came from using a full rate application of Fortress (quinoxyfen) at GS30 which impressed him by its persistence for up to 60 days. Next best was a two-spray strategy with kresoxim-methyl, although its usefulness will ultimately depend on its cost.

Other combinations of quinoxyfen at reduced rates with products such as Opus, Alto and Corbel showed its contribution but lacked the same persistence of effect as the full rate applications.

Unix (cyprodinil) as a first eyespot spray did not give mildew control but a combination with Fortress and Alto was better.

Mildew was still evident on plots treated with a conventional French programme – 0.8kg/ha Unix + 0.5 litre Alto at GS30 followed by 0.8 litre Opus + 0.5 litre Boscor at GS39. In the field, this would probably mean a third treatment with Caramba (metconazole), says Mr Maumené.

Azoxystrobin on its own seems to behave like an average triazole against mildew, says Mr Maumené.

Second best treatment on the Boigneville site comes, however, from 0.7 litre rates of Ensign (kresoxim-methyl + fenpropimorph) at GS30 and 39. "Ensign also gave good activity on septoria which is clear, as well as mildew, although the control is susceptible to timing," says Mr Maumené.

Good control was also obtained from tebuconazole (Horizon) at GS30 and 39, and from Alto + triticonazole. Moderate control came from metconazole (Caramba).

After disappointing results on mildew with fenpropimorph in recent years, ITCF is encouraging growers to move to fenpropidin.

A new Bayer material – spiroxamine – is giving experimental control similar to fenpropidin but is not a member of the morpholine grouping. Its performance mixed with tebuconazole (Folicur) is also similar to combinations of triazoles with morpholines.

ITCF is taking a number of its trial plots, in central and northern France, through to yield for publication later this year.


Upcoming webinar

What does the future of farming look like post Covid-19 and Brexit?

Register now
See more