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KEEP SPRAY INTERVALS TIGHT AND USE A STROB AT T2 TIMING
Date added: 16/05/08 |
Keeping fungicide spray intervals tight will result in an extra yield response of at least 0.3 tonnes/ha, valued at £45/ha with wheat at £150/tonne, according to three years of data from ProCam 4cast.
In 2003/2004 crops treated with fungicides applied at intervals of less than four weeks yielded on average 9.86 tonnes/ha, but when the interval was extended to more than four weeks the average yield was 9.48 tonnes/ha - a benefit of 0.38 t/ha. In 2004/05 the benefit of tighter spray intervals was 0.3 t/ha and 2005/06 0.31 t/ha extra, 4cast shows.
With less effective curative activity available in fungicides nowadays, it is important to ensure that fungicide treatments don’t run out of steam, says ProCam Group technical director Dr. Dave Ellerton.
“By keeping spray intervals tight you are, in effect, overlapping protection and making sure that green leaf area is maintained. If spray intervals are protracted, diseases will take hold and it is impossible to regain lost green leaf.”
Growers should aim for no more than four weeks between T1 and T2 and also between T2 and T3, he suggests.
“We are coming up towards key T2 timing in wheats and I would advise growers to apply their T2 once flag leaf is fully emerged, providing the interval is less than four weeks.”
“It is looking like a Septoria year, with some disease already on lower leaves, and if the warm conditions persist, it will turn into a rust year too. It is these diseases that need targeting at T2. For Septoria, products based on epoxiconazole or prothioconazole work well and for rusts those containing on cyproconazole and tebuconazole are useful, especially in curative situations.”
T2 is the key yield building timing and so it is the key timing for strobilurin fungicides, Dr Ellerton advises.
“Strobilurins are still having some beneficial effects on Septoria, around 20-30% control, and some strobs offer excellent rust control. In addition they result in physiological benefits and appear to help the crop overcome stress.
“According to BASF trials, when strobs were first brought out they were giving a 1.0 tonne/ha response. More recently the strob response has been around 0.3-0.4 t/ha but last year it was as high as 0.8 t/ha. Over the last ten years when pyraclostrobin was added to Opus, it has added on average at 0.66 t/ha, which is well worth having with wheat at £150/tonne.
“Syngenta trials show a similar response of 0.6 t/ha when azoxystrobin was added to a triazole and chlorothalonil at T2 timing.”
Dr. Ellerton advises the use of products such as Gemstone, a combination of epoxiconazole and pyraclostrobin as the ideal T2 treatment for wheat at flag leaf.
PRM184
16th May 2008
For further information please contact Dr David Ellerton, ProCam Ltd., Royston, Herts. Telephone: 01763 261592
Issued by Philip Hainey, Proterra Ltd., Stamford, Lincs. Telephone: 01780 756299
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