Influence of N‐fertilization and Fungicide Strategies on Fusarium Head Blight Severity and Mycotoxin Content in Winter Wheat

Abstract Nitrogen (N) fertilization and fungicide applications are still subject to discussion concerning the influence on Fusarium head blight (FHB) and related mycotoxin accumulation. Field studies were made in 2000–2001 and 2001–2002 to investigate the effect of two N‐rates and 11 plant protection treatments on FHB severity and the content of FHB‐related mycotoxins, namely deoxynivalenol (DON) and zearalenone (ZEA) under conditions of natural infection. The treatments applied can be summarized as (i) an integrated approach using a decision support system, (ii) the use of two plant strengtheners, Bion® (benzo [1,2,3]thiadiazole‐7‐carbothioic acid S‐methyl‐ester, BTH) and a compound based on the biomass of the cyanobacterium Spirulina platensis, (iii) the use of plant strengtheners in combination with a broad‐spectrum fungicide and (iv) common fungicide strategies against foliar diseases. Fusarium infections as well as the analysed mycotoxins were observed at low levels in both years. Disease severity was significantly increased by conventional N‐fertilization only in 2001. Neither FHB severity nor mycotoxin accumulation was significantly influenced by any of the treatments, although treatments without fungicides appeared to lead to lower disease severities. In 2002, there was a tendency towards higher disease severities when common fungicide strategies were applied. Mycotoxin contamination was found in grain samples from both years. In 2001 DON was mainly traceable, whereas in 2002 ZEA was also detected. Mycotoxin contamination was influenced by N‐fertilization rather than by the treatments. In 2001, the DON content was significantly increased due to the conventional N‐supply. Our results indicate that less intensive fungicide strategies, including plant strengtheners, are no worse than common fungicide strategies under conditions of low FHB severity and mycotoxin accumulation. Immoderate N‐fertilization however, can increase mycotoxin levels significantly even under conditions unfavourable for Fusarium spp.