A TEST METHOD BASED ON MICROSCOPIC ASSESSMENTS TO DETERMINE CURATIVE AND PROTECTANT FUNGICIDE PROPERTIES AGAINST SEPTORIA TRITICI

摘要

Glasshouse experiments to test the activity of commercial fungicides against Septoria tritici were carried out under controlled conditions. In addition to the parameter, % necrotic leaf area (NE), used to estimate the pathogen-induced leaf damage, the number of pycnidia per leaf (PYC) was determined to quantify the pathogen itself. Curative fungicide treatments were applied 100-210 day degrees after inoculation. A high curative activity was achieved up to 170 day degrees after inoculation, whereas the treatments at 200-205 day degrees were less effective. The best curative activity was observed for epoxiconazole-based treatments, followed by slightly less active azoles in the ranking tebuconazole, cyproconazole, prochloraz and flusilazole. Greater differences between the fungicides were observed for the protectant fungicide properties, which were tested 50-350 day degrees prior to inoculation. The best persistency was observed for epoxiconazole, whereas tebuconazole, cyprocoazole, prochloraz and flusilazole showed declining activity with this ranking. Combinations of triazoles with the active ingredients kresoxim-methyl and chlorothalonil, which are known to inhibit spore germination, significantly improved the longevity of the remaining green leaf area in comparison with disease-free treatments with triazoles alone. The results obtained under glasshouse conditions were compared with field studies on S. tritici development after treatments with tebuconazole to place the results in context. The comparison of the assessment parameter PYC and NEC between glasshouse and field trial showed that curative and protectant fungicide properties based on microscopic assessments of PYC in the glasshouse correlated well with results from field trials.