Monitoring and forecasting fungicide resistance in rhynchosporium

Abstract

Resistance has significantly reduced the performance of Bayleton, Bayfidan and Baytan against Rhynchosporium. This has probably occurred throughout most of the UK. A decline in sensitivity to propiconazole has also taken place, but Tilt/Radar still provide worthwhile Rhynchosporium control. However, Tilt exerted strong selection pressure again in 1990, and its use as a single product for Rhynchosporium control is not recommended. Changes in prochloraz sensitivity were small, and the performance of Sportak seems unchanged.

DMI/carbendazim mixtures continue to form the basis for combating any further development of DMI resistance, and these mixtures performed well. However, in 1990, well characterised carbendazim-resistant strains accounted for 1% of the total number of isolates examined suggesting that DMI/morpholine mixtures also need to be exploited for Rhynchosporium control.