Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2021 35 CONFERENCE REPORT A CROSS Europe growers are being encouraged to give greater thought to how they protect crops against early blight (Alternaria spp.) following the detection of isolates showing reduced sensitivity to fungicides belonging to the Quinone outside Inhibitor (QoI) mode of action group. Speaking at the Bayer Potato Conference via video link from his o ce in the Netherlands, Bert Evenhuis of Wageningen University & Research, reported that a novel genotype of Alternaria solani has shown itself to be more aggressive than wild relatives and less well controlled by products containing pyraclostrobin, azoxystrobin and famoxadone. Bert said the rising threat of early blight has increased steadily since the turn of the century as a changing climate has created conditions more favourable for the disease. E orts to protect crops has led to increased use of fungicides and in some cases, this has resulted in reduced sensitivity to certain modes of action. is has been hastened by a lack of breeding focus for Alternaria resistance in new varieties. Early blight spread warning e steady increase of Alternaria spp was a key focus at the 2021 Bayer Potato Conference, along with a three-point nematode plan. Isolates with reduced sensitivity to QoI fungicides were rst detected inGermany by researchers at the Technical University of Munich andmore recently in the Netherlands and other European countries. Most recently, research in Europe has identi ed reduced sensitivity to some SDHI active substances, namely boscalid. e challenge facing growers in seeking to protect crops is dealing with the two distinct species that make up the Alternaria complex. “Early blight is caused by Alternaria solani, the principal pathogen threat. Brown spot, usually also called early blight, is caused by Alternaria alternata, a secondary threat that enters the plant via earlier damage. Both species can be found wherever early blight is detected,” said Bert. Data sparce, but presence frequent Data on the prevalence of Alternaria spp. in the UK is sparse, but as many of those involved will attest, it is present in most seasons. “Developing more accurate decision support systems will be essential to promoting protection against both early and late blight.” Bert Evenhuis, Wageningen University & Research. ➜ The rising threat of early blight has increased steadily since the turn of the century