Flag leaf sprays – get vital
Wet weather and huge
disease pressure have
thrown cereal spray
schedules out of the
window. Andrew Blake finds
out how growers can best
retrieve the situation as the
crucial flag leaf spray timing
arrives across the country
AN unprecedented combination of conditions has made 1998 one of the hardest years in which to give crop protection advice.
Wet weather, thick crops and massive disease pressure have conspired to leave many crops well short of the protection they deserve.
With flag leaf emergence now underway it is more important than ever for growers to match product choice, rate and timing to disease pressure and crop yield potential and avoid inappropriate rate cutting, say agronomists.
One consultant who is particularly well placed to comment is West Sussex-based John Metcalfe. He is already well into preparing flag leaf recommendations for southern farmers using distributor Bartholomews of Chichester and manages a 320ha (800-acre) arable farm and dairy.
"It is not just the wet which has made it difficult to travel, we have had high winds and very high disease pressure resulting from early drilling and the mild winter."
Where growers managed to apply an early spray the range of T1 timings is probably wider than ever, making choice of subsequent treatments particularly tricky, says Mr Metcalfe. "We are competing with high levels of moisture in soils and high levels of disease in crops.
"In some winter barleys rhynchosporium and net blotch have been totally uncontrollable."
Strobilurin fungicides, where applied early enough, have done a good job, he reports. "I have about 2000 acres where they have worked well and crops look good. But there are tens of thousands of acres of heavy land in the east midlands where growers are having terrible trouble getting on."
The options from here on, as flag leaf emergence arrives, and in some places passes, centre around previous applications. But in every case the emphasis should be to avoid cutting corners, Mr Metcalfe advises.
With hindsight high levels of disease in crops which growers did treat early can largely be explained by dose cutting, he believes.
"The trouble nowadays is that there is no fixed pattern with early sprays. Many programmes are totally unplanned." That means a wide range of products including Opus (epoxiconazole), Pointer (flutriafol) and the newer Unix (cyprodinil) went on with no true idea of the real target, be it septoria, yellow rust or eyespot, he claims.
The perception that the most rewarding treatments come later has encouraged dose cutting, adds Mr Metcalfe. "Most people seldom go beyond half rates because they perceive that the second spray is where they should spend the most.
"That is generally the case," he admits. "But this year we have been caught out a bit."
In winter wheat there are three main scenarios each requiring a different approach, says Mr Metcalfe.
Flag leaf sprays need careful planning if foliar disease is to be controlled at lowest cost this season, says agronomist John Metcalfe of Bartholomews (right) seen here with Phillip Gurney of Old Place Farm, Angmering, West Sussex. This Soissons had a flag leaf spray of 0.7 litres/ha of Mantra.
FLAG LEAF SPRAYS
• High disease pressures, but high yield potential too generally.
• Three main strategies in wheat:
T1 well timed and successful,
T1 late and struggling,
T1 not on yet.
• Limited role for strobilurins.
• Rhynco & net blotch rife in barley.
• Late pgr inclusions?