New aspects in use of fungicides for control Fusarium head blight

Fusarium head blight (FHB) caused by Fusarium graminearum (Schwabe) and Fusarium culmorum (W.G. Smith Sacc.) belongs to the most damaging diseases in cereal crops. Actually mycotoxin contamination of human food and animal feed became a more important feature than direct yield losses that often occur irregularly. F. graminearum and F. culmorum were described to produce Deoxynivalenol (DON), but also ability to produce DON derivates and zearalenone has been recognized in some isolates of both species. These trichothecenes are phytotoxins and causes chlorosis, necrosis and wilting. The aim of contribution was to estimate efficacy of new fungicide for controlling fusarium head blight in wheat. Additionally the protective and curative effects of fungicide compounds were tested. For measuring the efficacy severity and incidence was assessed. Also the yield, fusarium damaged kernel (FDK) and Deoxynivalenol-content in grains were determined. The investigations were performed in field trials over two years using artificial inoculation methods and a randomized block design with four replicates. For testing the fungicide efficacy maize residues / debris were applied as an inoculum source. They were distributed on the plots in winter months. Spray inoculation was used for investigation of protective and curative fungicide effects. In addition to natural inoculum, plots were inoculated with 250.000 conidia /ml of F. culmorum at mid anthesis. Fusarium severity and incidence was determined 21, 24 and 28 days after inoculation. After harvest, yield, DON concentration and fusarium damaged kernels were quantificated.For reduction of fusarium head blight prothioconazole, tebuconazole and the tank mix of epoxiconazole + metconazole resulted in the best efficacy levels of 70-90%. Comparing these data with DON reduction so a high correlation (r = 0.86; P = 0.01) was determined. As a new fusarium fungicide thiophanate-methyl produced a positive effect on DON-reduction while the reduction of visible symptoms was only moderate. Analyzing the treatments for optimal fungicide timing spraying 36-48 hours after inoculation showed the best efficacy of 80-90%. Applications days before inoculation the disease control was reduced nearly 10-20%. The efficacy to control fusarium head blight was improved by mixing the triazoles with morpholines (SBI, class II, amine). A faster uptake of the active ingredient could be provided.In all fungicide treatments an incremental yield was measured.The study demonstrated a positive linear relationship between DON and Fusarium head blight reduction by using modern new fungicides.