The occurrence of Erysiphe trifolii on Lathyrus pratensis in a foothill area of South Bohemia

The aim of small-site experiments carried out in the foothills of the ?umava Mts. was to determine the effect of the etiological agent powdery mildew (Erysiphe trifolii) on meadow peavine (Lathyrus pratensis). Over three consecutive years, we observed a whitish to greywhite soft cover of mycelium on the meadow peavine during the vegetation period. This characteristic symptom of the disease was observed on the plants during summer and autumn. In a plot trial with permanent grassland we evaluated the following management systems: i) mulched, ii) fallow, iii) mown stands, and iv) pasture stands grazed by cattle. We evaluated the total number of Lathyrus pratensis plants as well as the number of the plants attacked by Erysiphe trifolii. The three-year investigation of Lathyrus pratensis yielded statistical evidence that the most significant growth of the fungal disease was recorded in fallow stands (68.9%), while the lowest occurrence of the disease (4.4%) was found in the pasture stands grazed by cattle.