Strobilurin + triazole fungicide will maximise beet yield
With every beet from the 2011 crop counting at full price theres every incentive to maximise yield. An extensive series of trials has shown that using a new generation strobilurin + triazole fungicide will get the best yield response.
In the trials undertaken by Broom’s Barn, British Sugar and Bayer CropScience from 2007 to 2010 beet that did not receive a fungicide spray averaged 77 t/ha. A straight triazole spray (flusilazole) added 3 t/ha and the strobilurin + triazole fungicide Escolta (trifloxystrobin + cyproconazole) added 8 t/ha, which was 2.6 t/ha ahead of the nearest competitor Spyrale (difenoconazole + fenpropidin).
Agrovista technical manager Mark Hemmant confirms the results reflect his field experience. Of the three strobilurin + triazole options Escolta, Opera (pyraclostrobin + epoxiconazole) and Priori Xtra (azoxystrobin + cyproconazole) best yield responses come from Escolta and its the only one priced as a dedicated sugar beet fungicide, so growers gain on both sides of the cost-effectiveness equation.
Furthermore he says there is now a strong case to consider a two-spray strategy on later lifted beet for extended disease control, frost protection and yield maximisation. In 15 of the trials where one and two sprays were compared a second (T2) Escolta spray added a further 4.2 t/ha.
According to the British Sugar 2010 survey the area receiving two sprays jumped to 38% from 21% in 2009. However, Mark Hemmant now advises a two-spray strategy as standard practice on any beet destined for lifting beyond the end of October. Considering the campaign length, two thirds of crops should benefit from T2 sprays; those not getting them may under perform by up to 70/ha in gross margin.
Dr Mark Stevens, head of crop protection at Brooms Barn says there are already signs that broad-spectrum protection will be key this season.
The powdery mildew forecast is for 49% of the crop to be affected by the end of August (based on ground frosts in February and March): thats much higher than the last two seasons. Early in May we also saw rust starting to sporulate on overwintered field-grown beet at Brooms Barn as part of an experiment. This may be an indication of high rust pressure to come later in summer.
The fact that two unexpected foliar disorders late black leaf effect and yellow beet syndrome affected plots at Brooms Barn last year, where no fungicide or only one spray was used, adds to the case for broad-spectrum control and consideration of a two-spray strategy this season, he says.
BBRO recommendations for 2011 are to keep a close eye on crops from the middle of July and apply a full rate broad-spectrum fungicide at the first sign of disease onset. Advice on the need for T2 sprays will be issued nearer the time via the BBRO bulletin.
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