Dunker, S., Tiedemann, A. v. Institute of Plant Pathology and Plant Protection, Georg-August-University Goettingen, Grisebachstr. 6, 37077 Goettingen, Germany
Sclerotinia sclerotiorum is the most important fungal pathogen in German winter oilseed rape production. Due to an increasing acreage of oilseed rape, the crop rotation diseases such as Sclerotinia stem rot are becoming more important. In many growing areas preventive fungicide treatments are carried out at bloom stage to control this disease, which results in a high frequency of treatments, many of which are not cost efficient. In order to reduce inefficient fungicide sprays, a crop loss prediction model has been developed which involves damage thresholds of the disease. Crop loss induced by Sclerotinia sclerotiorum was analysed in a three-year field experiment. In the field trials different determinants of the disease such as inoculation date, level of infestation, sowing time, seed density and rapeseed cultivar were examined by artificial inoculations of rapeseed plants with the “toothpick method”. In addition the cost effectiveness of fungicide sprays against Sclerotinia sclerotiorum was evaluated on the basis of data available from the German state extension services since 1991. The results of the field trials of the first two experimental years show that crop losses primarily depend on the time point of inoculation (early/late blossom) and the cultivar (line/hybrid). Infections at early bloom resulted in higher yield losses than infections at the end of bloom. Economic damage thresholds justifying fungicide applications were significantly higher in the hybrid than in the line cultivar. In another field trial the compensation potential of winter oilseed rape was examined. About 40% of plant losses at the end of bloom could be compensated, basically due to an increasing thousand seed weight. The economic evaluation of fungicide sprayings against Sclerotinia sclerotiorum revealed about 67% of applications being economically inefficient. The mean yield of fungicide sprays was 2.41 dt/ha and did not cover the average costs of a fungicide application, which is equivalent to 3.32 dt/ha. Based on the results of the field trials and the economic evaluation an economic damage threshold has been developed which will be implemented in the crop loss prediction model.
Biological control of wheat and barley against phytopathogenic fungi
Josef Hysek, Milan Vach, Jana Brozova
Research Institute of Crop Production, Drnovska 507, Prague 6 - Ruzyne, Czech Republic
Biopreparations present a new way for plant protection against fungal diseases. These biopreparations are based on antagonistic microorganisms which depress pathogenic fungi transferred by the plant (systemic infection) or by the soil. We used biopreparations of Czech provinence: Supresivit (based on the fungus Trichoderma harzianum), Polyversum (based on the fungus Pythium oligandrum) and Ibefungin (based on the bacteria Bacillus subtilis). The means of application were by seed treatment, and application with mineral fertilizer directly to the soil. For control purposes, we used the chemical seed protectant Vitavax 200 WP (carboxin, thiram). We used the following varieties: EBI (winter wheat) and Akcent (spring barley). The presence of phytopathogenic fungi in the soil was controlled by cultivation methods (method of soil extract) in these field variants (4 rep.) on the basis of 4 years experiments. The dose of Vitavax was 2.5 l/t of the seed and the dose of biopreparates was 1mg/kg of fertilizer or seed. Health state of the plants treated with the biopreparations was better than in the controls. We found that in treated parcels the plants were less contaminated with phytopathogenic fungi: Septoria spp., Drechslera spp., Pyrenophora spp., Mycosphaerella spp., Leptosphaeria spp., Fusarium spp., Rhynchosporium secalis), and some of them were transferred by the soil. The soil of treated variants contained smaller quantities of named phytopathogenic fungi. The yields from the variants treated with biopreparations were higher, about 3-5 % above the value of the control.
Biological control practices
Claude Alabouvette, INRA UMR “Microbiologie Géochimie des Sols”BP 86510, 21065 Dijon Cedex
Biological control of plant diseases has been studied for many years. Baker and Cook published the first book entirely dedicated to biological control in 1973. Since that time numerous research papers, several books and review article have been produced, but practical application of biological control remains confidential. Today there is a renewed interest for biological control practices or for what is sometimes called “alternative methods” of disease control. These methods include not only the use of biological control agents but also the prophylactic methods, the use of natural substances triggering the plant defence reactions, and the use of cultural practices having a beneficial effect on plant health. It must be recall here that any type of measure enabling to prevent the introduction of a pathogen or to prevent the development of the disease must be