No abstract

The impact of nitrogen (N) fertilization on the development of Fusarium head blight (FHB) in wheat and the resulting deoxynivalenol (DON) contamination in the kernels was studied. In a first experiment, the disease was assessed on two locations under natural infection pressure. Five different types of nitrogen fertilizer (both organic and mineral) were investigated, each applied at five input rates from 0 to 160 kg N/ha. With all fertilizers, a significant increase of disease intensity was observed with increasing N input, while the type of N fertilizer had poor or no effects on FHB. Depending on the fertilizer used, the percentage of diseased spikelets increased from 2.2% at zero N rate up to 6.6% at 160 kg N input per hectare. In a second series of trials, three spring wheat varieties including one Durum wheat line were artificially inoculated with a Fusarium graminearum and a F. culmorum strain, known producers of DON. A mineral N fertilizer was applied at five input levels from 0 to 160 kg N/ha. A significant increase in FHB intensity and DON contamination in the grain was observed with increasing N from 0 to 80 kg/ha. At higher input rates, relevant in contemporary crop husbandry, disease intensity and toxin contamination remained at constant levels. It is concluded that adaptation of N fertilization represents no relevant tool in managing FHB in practical wheat cultivation.

A representative survey was made of maize ears of the 1988 and 1989 crop in Austria to establish the influence of corn borer injuries onFusarium species involved in ear fusariosis andFusarium toxin production.TheFusarium species most frequently isolated from rot-damaged ears wereFsacchari var. subglutinans (about 50 %) andF. graminearum (about 30 %). There was a striking difference between theFusarium species of the Liseola and the Discolor section concerning their occurrence on corn borer-damaged ears. More than 80 % of the ears infected withF. sacchari var. subglutinans andF. verticillioides, but less than 15 % of the ears infected withF. graminearum, F. crookwellense andF. culmorum showed corn borer injuries.Toxin analyses of the infected ears corresponded to the known toxigenicity of the respectiveFusarium species. Ears infected withF. sacchari var. subglutinans contained moniliformin (up to 20 mg/kg), those infected withF. verticillioides fumonisin B1 and B2 (up to 15 mg/kg). In ears infected withF. graminearum, F. culmorum andF. crookwellense zearalenone (up to 40 mg/kg) and deoxynivalenol (up to 500 mg/kg) or nivalenol (up to 10 mg/kg), respectively, could be detected. Hence measures to combat the European corn borer will mainly reduce moniliformin and fumonisin contamination, but will affect zearalenone, deoxynivalenol and nivalenol contents of the ears to a much lesser extent.

Fusarium subglutinans has been identified as a prevailing pathogen of maize ears in Poland in the seasons 1985-1991. About 95-100% of ears with Fusarium ear rot symptoms were infected by this species. Moniliformin was present in all 57 ears with pink ear rot symptoms examined. Fusarium-damaged kernels contained an average of 130.9 mg/kg of moniliformin, with large differences between individual samples each year--from 4.2 mg/kg to 530 mg/kg.

Fusarium avanacoum infected wheat and triticale heads in Poland in each season between 1985 and 1989. The average number of heads infected byF avonacaum was 26 % for wheat and 46 % for triticale out of all examined heads withFusarium head blight symptoms.Fusarium-damaged wheat grain, naturally infected byF avenaceum, contained an average of 15.9±7.7 mg moniliformin/kg, healthy looking kernels from the same heads an average of 0.42±0.19 mg moniliformin/kg. Fusarfum-damaged kernels of triticale contained an average of 3.5 mg moniliformin/kg while healthy looking kernels from the same ears contained 0.25 mg/kg.