Heavy rain and thunderstorms across southernand eastern England could trigger the onset of foliar diseases in maize crops.Cool wet or humid conditions typically result in more serious loss of greenleaf area caused by Eyespot and Leaf Blight,at a time when crops should be growing at their fastest, warns Syngenta FieldTechnical Manager, Simon Roberts.
After a slow start, most maize crops havebeen growing incredibly well, he reported. For many, the height of plants issuch that now is the last opportunity to spray a preventative fungicide usingconventional farm sprayers without causing damage.
Leaf diseases that result in early die-backof plants can severely affect yields of forage maize and feedstock for biogasproduction. This season is the first time UK growers have a fully approvedfungicide for use in maize, with Quilt Xcel.
Mr Roberts advocates that enhancing maizeplant health and protection of the green leaf area with Quilt Xcel ensures thecrop can make more effective use of sunlight to boost cob yield. Yieldimprovements of over 15% have been seen in trials from the control of LeafBlight alone.
The label recommendation for Quilt Xcel isfor 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 preventativefungicide, targeted to protect the leaf from infection ahead of high riskconditions – typically at an earlier timing, he added.
Later application, in taller crops, is likelyto require specialist high clearance spray equipment. That may require a contractor, although MrRoberts highlighted many arable farms growing biogas maize will currently havesprayers kitted out for oilseed rape desiccation that would give greater cropclearance.
He pointed out that operators should aim for50cm boom height clearance above the crop, with the use of angled nozzlespotentially giving better coverage into the canopy. He reported new Syngentanozzle technology and application trials could give growers further options toextend spraying opportunities in the future.
Although most spraying operations are nowgeared to speed, where sprayers are going through taller crops much of thedamage can be alleviated by slowing down; allowing the crop to bend over andthen spring back, rather than snapping off, he advised.
However, any sprayer damage is likely to beminimal, compared to the losses from an outbreak of disease stripping leavesand decimating yield.
Northern Leaf Blight (Helminthosporium turcicum) has only been identified in the UKrelatively recently, however climatic conditions and the increase in industrialmaize 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 leafloss.
Early infection at or before flowering canresult in up to 50% yield loss, but if leaves can be kept clean for severalweeks post flowering from a Quilt Xcel treatment, any late infection will havelittle or no effect on final yield.