OILSEED rape growers have been warned about the danger of Sclerotinia affecting crops much earlier this year.
Dr Caroline Young, from ADAS, says this year’s crops are up to a month ahead of the same time last year, with some plants flowering super-early.
Their advanced state is due to recent unseasonably warm weather but accompanying that is a significantly earlier Sclerotinia risk compared to spring 2013.
Dr Young said farmers are close to the expected appearance of the Sclerotinia fungal fruiting bodies (an apothecium).
The apothecia are already present, or expected to appear imminently in some areas.
This is in stark contrast to what was seen even as late as May last year.
Generally the South West warms up first and the North- East last, but Dr Young said there will be variation with local topography and conditions.
She recommended growers in all areas to review their crop risk and plan their fungicide strategies accordingly.
Dr Young said: “Most areas on a predictive map are now red, which agrees with what we are observing at BASF’s Sclerotinia monitoring sites, where germination has now started in all depots.
“Any crops at early or midflower, which are in red areas, should be considered at risk from infection and it is likely that foliar fungicide applications now may be justified.
“Crops in the remaining orange areas will also be at risk shortly, so fungicide treatment now will also be beneficial, assuming a three week protection window for fungicides, under normal conditions.”
Crops at late flower may also benefit from fungicide treatment.”
They are still at risk, but late infection tends to affect more of the lateral branches and therefore not be so damaging to yield as infection that occurs early and affects the main stems.”
If lodging occurs, infection at any flowering phase can spread rapidly through a crop by plant to plant spread.
In terms of timing, the main difference for growers compared to 2013, is the calendar dates for early flower fungicide applications – growers will need to be applying fungicides now, or have already applied them, rather than in April or May.
“The usual guidelines for fungicide timing according to susceptible crop stage (open flowers), inoculum risk (sclerotial germination observations and predictions, and/or petal tests) and weather conditions (warm, light rain) will still apply,” said Dr Young.
“However 2014 conditions have seen fungicides being applied earlier, where, if no other guidelines are taken into account, oilseed rape flowering began early and continues to progress earlier than in most years.”
BASF’s Sarah Mountford- Smith recommends that for applications targeted at Sclerotinia, growers should use Filan (boscalid) at 0.3-0.5 kg/ha, applied ideally before petal fall.
“Both Filan and prothioconazole- based fungicides give excellent control of Sclerotinia, but, importantly, HGCA trials have shown that Filan consistently contributes a yield increase in the absence of disease.”
“It is also a different mode of action for resistance management of Light Leaf Spot, at a time when triazole resistant strains of Light Leaf Spot exist, and since spores will still be present in the crop. And finally, Filan is ‘Bee-safe’; it can be mixed with pyrethroids for seed weevil control at flowering when bees are not foraging.”
To join BASF/ADAS Sclerotinia Outlook e-Alert list, register at agricentre.basf.co.uk.