Very forward oilseed rape crops may need two applications of growth regulation this autumn, while crops in dry areas have the oppostie problem.
Good establishment conditions mean some crops drilled in the middle of August have three true leaves already in parts of the south, West Midlands and the north-east where crops were drilled early into fallow ground, says Richard Elsdon, United Oilseeds‘ technical manager.
That’s causing concerns about excessive leaf development and height, he suggests. “While these big plants have an advantage in overcoming weed competition and pigeon damage, previous experience shows very advanced crops don’t produce good yields.”
It means growers should consider autumn growth regulation to ease management, he says. “Using a triazole fungicide will have two effects – it puts the brakes on plant growth and it enhances root development, helping it to scavenge for nitrogen.”
Timings and rates vary with product choice and individual field conditions, he notes. “It’s important to discuss strategy with your agronomist. Get out in the field, do the plant counts and consider the options.”
But not all growers have been so lucky, says Graham Brooks of Prime Agriculture. In his part of Essex dry weather has held back crop development meaning growth regulation is unlikely to be needed. “We’ve hardly got a crop here.”
Only a minority of crops in East Anglia are very forward, his colleague in Norfolk, Peter Riley, agrees. “The early August drilled crops are forward, but crops drilled a week or two later are only at cotyledon having germinated when we had rain around two weeks ago.”
Those very forward crops will need a check this autumn, he says. “But generally the greater growth regulatory effects are seen from spring applications.”
In Bedfordshire Bob Mills of Frontier is cautiously optimistic that growth regulation might be necessary this autumn in some crops, but says very few are so far advanced yet. “It has been unbelievably dry but the difference between this year and autumn 2007 is that there was moisture underneath this year, which if the seed chitted has been enough to keep crops going.”
BASF advice for metconazole-based products on very forward crops is to apply the fungicide from the two- to three-leaf stage.
“That’s a bit earlier than the four- to six-leaf stage recommended for standard crops,” admits the firm’s Clare Tucker. “But it will allow growers to tank mix it with a graminicide, if necessary.”
Where metconazole is going to be applied later, rates will need to be adjusted, notes Mr Elsdon. “There may even be a case for two applications. Crops drilled in August which then benefited from the rain and warm temperatures are romping away.”
For tebuconazole-based sprays, Tim Nicholson of Bayer CropScience recommends spraying in early to mid October, when crops are at five true leaves. “This will give the better rooting and prostrate plant habit required for the winter. But don’t forget to add a phoma-active fungicide to the programme too.”
Any later drilled crops sown in the second half of September will benefit from between 15-25kg/ha of nitrogen in the seed-bed, he adds. “It needs to be applied ahead of the drill and you mustn’t exceed the 30kg/ha limit.”
Watch out for insect pests
Be alert for signs of flea beetle and turnip sawfly larvae in newly emerged oilseed rape crops, especially where farm-saved seed or broadcasting establishment techniques have been used.
Turnip sawfly larvae activity has already been reported in Dorset, a likely consequence of the warm temperatures, says Duncan Woodward of Syngenta.
“They are the same conditions that favour flea beetle,” he says. “And it’s coinciding with crop emergence in the excellent growing conditions.”