Heavy rain and thunderstorms across southern and eastern England could trigger the onset of foliar diseases in maize crops. Cool wet or humid conditions typically result in more serious loss of green leaf area caused by Eyespot and Leaf Blight, at a time when crops should be growing at their fastest, warns Syngenta Field Technical Manager, Simon Roberts.“After a slow start, most maize crops have been growing incredibly well,” he reported. “For many, the height of plants is such that now is the last opportunity to spray a preventative fungicide using conventional farm sprayers without causing damage.”Leaf diseases that result in early die-back of plants can severely affect yields of forage maize and feedstock for biogas production. This season is the first time UK growers have a fully approved fungicide for use in maize, with Quilt Xcel.
Mr Roberts advocates that enhancing maize plant health and protection of the green leaf area with Quilt Xcel ensures the crop can make more effective use of sunlight to boost cob yield. Yield improvements of over 15% have been seen in trials from the control of Leaf Blight alone.The label recommendation for Quilt Xcel is for one application of 1.0 l/ha, at any time from stem elongation (GS 30) through to the end of flowering (GS 69). “Quilt Xcel is a preventative fungicide, targeted to protect the leaf from infection ahead of high risk conditions - typically at an earlier timing,” he added. Application adviceLater application, in taller crops, is likely to require specialist high clearance spray equipment. That may require a contractor, although Mr Roberts highlighted many arable farms growing biogas maize will currently have sprayers kitted out for oilseed rape desiccation that would give greater crop clearance. He pointed out that operators should aim for 50cm boom height clearance above the crop, with the use of angled nozzles potentially giving better coverage into the canopy. He reported new Syngenta nozzle technology and application trials could give growers further options to extend spraying opportunities in the future. “Although most spraying operations are now geared to speed, where sprayers are going through taller crops much of the damage can be alleviated by slowing down; allowing the crop to bend over and then spring back, rather than snapping off,” he advised.However, any sprayer damage is likely to be minimal, compared to the losses from an outbreak of disease stripping leaves and decimating yield. Northern BlightNorthern Leaf Blight (Helminthosporium turcicum) has only been identified in the UK relatively recently, however climatic conditions and the increase in industrial maize cropping is expected to see the incidence worsening over coming years, said Mr Roberts. “Humid conditions appear most conducive to rapid infection; initial spots can spread by over 1cm in just 24 hours, leading to rapid leaf loss.”Early infection at or before flowering can result in up to 50% yield loss, but if leaves can be kept clean for several weeks post flowering from a Quilt Xcel treatment, any late infection will have little or no effect on final yield.