Fungicide impact on yield and Ramularia leaf spot, fungal biomass and rubellins

摘要

Ramularia leaf spot (RLS) has been recognised in Denmark since 2004 as a common disease in barley production. A factorial field trial in winter barley with three different fungicides and three different timings of application investigated the impact on RLS, fungal biomass of Ramularia collo-cygni using ELISA, content of rubellins B and D using HPLC and yields of grain. Fungicides containing epoxiconazole were better at controlling RLS, fungal biomass and rubellins compared with the mixture picoxystrobin + cyprodinil. The two earliest application times (GS 37-39 or 51-55) controlled fungal biomass and increased yields best compared with a later timing (GS 65). Correlations between visual assessments of RLS severity and the amount of fungal biomass and rubellins were both significant with R~2=0.68 and R~2=0.80 respectively, which indicates that rubellins play a major role for the symptoms observed. The correlation coefficient between fungal biomass and rubellins was also significant with R~2=0.61, which might reflect that other factors contribute to the variability. The correlation coefficient between visual assessments of RLS and yield revealed a poor correlation (R2=0.23) indicating that even though fungicides apparently controlled RLS, the impact on yield was only minor.