Dynamics of spread and control of cercospora (Cercospora beticola Sacc.) and ramularia (Ramularia beticola Fautrey and F.Lamb.) leaf spot in sugar beet crops

Abstract

Dynamics of spread of the most destructive sugar beet foliar diseases cercospora (Cercospora beticola Sacc.) and ramularia (Ramularia beticola Fautrey & F.Lamb.) leaf spot and efficacy of six fungicides used for their control were investigated at Rumokai Research Station of Lithuanian Research Centre for Agriculture and Forestry during 2011–2012. The crop was sprayed with fungicides once after the first symptoms of foliar diseases had been spotted. In the experimental years, cercospora leaf spot started to spread in the sugar beet crops on the 31st of July – 3rd of August. During the 1st assessment the disease incidence was 4.3–19.2% and the disease severity was 0.01–0.08%. Further progress of cercospora leaf spot was influenced by the weather conditions: with the weather being wet and warm the disease development was rapid and 10–11 weeks after the 1st assessment the disease incidence reached 90.0–98.3%, and the disease severity was 10.98–11.91%. Ramularia leaf spot started to spread at the same time as cercospora leaf spot; however, its severity was lower. The progress of ramularia leaf spot was weaker than that of cercospora leaf spot and before harvesting ramularia leaf spot severity reached 1.75–1.79%. The highest efficacy against both diseases was exhibited by the fungicides containing epoxiconazole – Maredo, Opera N, Tango super.