Sugar beet fungal disease cercospora beticola found in Suffolk - one of first cases confirmed in UK

Cercospora leaf spot.

Cercospora leaf spot. - Credit: Archant

A sugar beet fungal disease has been discovered at a Suffolk site.

The discovery of the first cases in the UK of QoI-resistant Cercospora beticola, which causes Cercospora leaf spot in the crop, is “concerning”, said British Beet Research Organisation (BBRO) lead scientist Dr Mark Stevens, but needed to be kept in context, as other diseases posed more of a threat.

Samples taken from infected beet plants at sites in Suffolk, Lincolnshire and Cornwall as part of routine resistance monitoring by agricultural chemicals firm Bayer in 2016 were found to be resistant to its QoI (quinone outside inhibitors) fungicide, trifloxystrobin.

“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,” said Dr Stevens.

“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).”

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Bayer said trifolxystrobin was co-formulated, or combined, with cyproconazole in its Escolta product.

Bayer campaign manager for root crops, Edward Hagues, said 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,” he said.

“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.”