Erarbeitung von Schwellenwerten zur gezielten Bekämpfung von Zwergsteinbrand (Tilletia controversa) und Steinbrand (Tilletia caries) sowie deren praktische Umsetzung im Öko- Landbau

Abstract

Dwarf bunt of wheat (Tilletia controversa) and common bunt of wheat (Tilletia caries) are the most important pathogens in organic cereal production. The aim of this research work is to find out whether a threshold value for seed is sufficient or whether the infection potential in the soil must be considered additionally. For dwarf bunt of wheat two-years-lasting field trials are performed at 3 sites with susceptible and low-susceptible wheat and spelt cultivars, 4 infection levels and 4 replications. The field trials are designed in a randomized split-block design with additional marginal-plots, so (1) sowing and harvest will be possible without greater interaction between the field plots, (2) spore contamination of the soil during harvest will be assured and (3) the determination of spore inoculum density in the soil after harvest will be enabled. Only fields with natural spore contamination are chosen. The field trials for common bunt of wheat are carried out in a similar design with 4 replicates at 4 sites with susceptible and low-susceptible wheat cultivars and two different sowing times. For an infestation with dwarf bunt of wheat, diffuse light is sufficient. The wheat cultivar Capo showed a significantly lower infestation than the cultivar Saturnus. The infestation of the spelt cultivar Franckenkorn was significantly lower than that of the cultivar Oberkulmer Rotkorn, with the infestation of spelt cultivars being in principle lower because of morphological features. The greatest significant number of infested spikes per m² was found in the variant soil infection. With the dwarf bunt of wheat results from the first year no threshold values can be determined neither for seed nor for soil. In the case of infestation with common bunt of wheat, there were no significant differences between the early and late sowing dates, nor between the cultivars Capo and Tommi. The highest bunt spore potential in the soil was found at the field trial site in Saxony; however, the highest number of infested spikes per m² was not found there