The first cases of fungicide-resistant Cercospora beticola, the fungal disease that causes Cercospora leaf spot in sugar beet, have been identified in the UK.
Samples were taken from infected beet plants at sites in Suffolk, Lincolnshire and Cornwall as part of routine resistance monitoring by Bayer in 2016.
All three were found to be resistant to the company’s QoI fungicide trifloxystrobin.
QoI, or quinone outside inhibitors, are a group of fungicides used in agriculture.
Trifolxystrobin is co-formulated with cyproconazole in Bayer’s product Escolta. The Bayer campaign manager for root crops, Edward Hagues, says that one of the main purposes of co-formulation is resistance management.
“Triazole fungicides are unaffected by this resistance and will continue to provide protection against the disease. The best fungicide programme for beet continues to be two Escolta sprays at 0.35L/ha, giving excellent control of the major sugar beet diseases – powdery mildew and rust – and a proven yield-boosting effect.”
'Concerning'
British Beet Research Organisation (BBRO) lead scientist Dr Mark Stevens acknowledges that the finding is concerning, but says it needs to be kept in context.
“These were three samples, taken in one year and collected as part of a large-scale European monitoring programme, and does not mean there has been an escalation in the threat level posed. Further analysis is required to determine the extent and significance of this finding.
“Cercospora usually occurs infrequently and at low levels in the UK because our cooler weather is not conducive to its development. When it is seen, it is usually later in the season, when it has less impact on yields. Good crop hygiene is important to minimise the risk of future disease carryover.”
He added: “While Cercospora can be a serious disease and is widespread across Europe it is not the principal disease threat to crop performance in the UK or the primary target of fungicide programmes, so while growers should remain vigilant, powdery mildew and rust should remain the focus (of programmes),” he said.
