Light exposure to develop heavy OSR yields
With Syngenta iOSR group oilseed rape growers reporting crops, for the most part, having established strongly and come through the winter well, thoughts have turned to how to make the most of the potential for the coming season, reports Syngenta Field Technical Manager, James Southgate.
“Growers in the dry eastern areas or Flea Beetle hotspots have once again suffered very badly with establishment, with many fields extremely patchy, or lost entirely,” he reported. “But those crops that got away, typically having a strong foundation.”
He advocated iOSR growers should be looking to build on crop structures to ensure they make best use of available sunlight. “Last year really highlighted the issues of low light capture through a dull growing season, which reflected in disappointing yields at harvest.
“However, growers can manage the height and shape of plants with Toprex PGR treatments to ensure light can penetrate to lower leaves, to convert into the energy reserves that will drive yield.”
James (below) detailed results of research trials and growers’’ experiences that showed application at early stem extension (GS31) would prove the most effective in suppressing extension of the main raceme and encouraging even plant development with a more efficient open structure.
“Furthermore, the treatment synchronises the plant’s development and flowering, so you get a visible consolidation of the flowering period into a shorter time span," he said.
"The result is less light reflectance by the yellow flowers, which means more is available for the plant to utilise and drive yield.”
He pointed out that a further benefit would typically be a reduction in time the crop is under pressure from Pollen Beetle and Sclerotinia, as well as evening up the crop for easier harvesting. “For more backward crops, where growers may not want to regulate early recovery growth, Toprex could still be applied to enhance structure right through to GS51-55, but any height reduction would be limited.”
Light Leaf Spot activity
James added that the combination of fungicide activity in Toprex also provided a useful role in the Light Leaf Spot control programme. Independent trials last spring had shown activity was equal to prothioconazole or tebuconazole, with a combination of reduced rate Toprex and low-rate tebuconazole proving especially effective in the high pressure season.
He pointed out that whilst incidence of LLS (above) had remained low so far this season, growers must be ready to treat at the first signs of infection.
“Risk will be dependent on many factors, not least the use of Phoma treatments last autumn that are also the first stage tackling LLS; crops that were treated early will be at higher risk than those that received a late treatment,” advised James.
iOSR meeting growers reported a universal one-spray strategy for Phoma control last autumn, with practice evenly spread between those targeting an early solus treatment at first incidence of disease, followed up by a propyzamide grassweed treatment, and those who delayed Phoma application to combine both treatments in one pass.
“If crops remain clean through to stem extension Toprex PGR timing, then that application alone could suffice,” he believed. “But if outbreaks do occur before that, growers shouldn’t delay with a LLS specific treatment.”