Go for green with OSR leaf
Sclerotinia can have a devastating hit on oilseed rape yields in a high pressure situation. It is more than a decade since the last serious national outbreak, but there are still reported incidences every year.
Where growers have a history of sclerotinia incidence on the farm, particularly when the season conspires to create disease pressure - typically with warm, wet weather through the flowering period - Syngenta’s Georgina Wood suggests growers will benefit from additional benefits of green leaf retention with Amistar, alongside its disease control.
“This season the greening effect could be particularly important to help crops recover from the impacts of cabbage stem flea beetle larvae damage,” she advised iOSR growers. “In many instances crops have shed large numbers of leaves where the petioles have been damaged.
“They will now be reliant on compensatory new growth, to capture sunlight and fill seeds with oil.”
Furthermore, Georgina warned that the larvae damage has created widespread variability between plants, which is anticipated to lead to an extended flowering period.
NIAB has already warned growers of the protracted flowering period, which it reports may need a two or even three spray disease control strategy.
With a target 6000 to 8000 pods per m2, Georgina pointed out that OSR seed yield is determined by the amount of photosynthesis carried out by the crop during a 19 - 25 day period after mid-flowering, with green leaf the primary source of energy for seed fill.
ADAS trials have shown that a single Amistar application can maintain an additional 0.5 GAI 10 days after end of flowering and still 0.25 greater GAI 20 days later.
“Timing of fungicide applications is going to be important this season,” she suggested. “If sclerotinia risk rises, then the conventional early to mid-flowering prevention will be crucial."
"But growers will also still likely gain from later applications, targeted at healthy green leaf retention and preventing leaf spot infections.”
In both instances, she believes the greening effect of Amistar will boost the essential oil content of seed and overall returns for growers.
Sclerotinia key risk factors:
Wet and warm conditions
OSR crops in flower
Length of rotation, including other host crops
Presence Sclerotinia spores
Fungicide programme applied
Relative humidity >80% + Air temperature >7°C + >23 hours duration = Greatest risk of sclerotinia infection
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