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

Glasshouse experiments to test the activity of commercial fungicides a gainst Septoria tritici were carried out under controlled conditions. In addition to the parameter, % necrotic leaf area (NE), used to estim ate the pathogen-induced leaf damage, the number of pycnidia per leaf (PYC) was determined to quantify the pathogen itself. Curative fungici de treatments were applied 100-210 day degrees after inoculation. A hi gh curative activity was achieved up to 170 day degrees after inoculat ion, whereas the treatments at 200-205 day degrees were less effective . The best curative activity was observed for epoxiconazole-based trea tments, followed by slightly less active azoles in the ranking tebucon azole, cyproconazole, prochloraz and flusilazole. Greater differences between the fungicides were observed for the protectant fungicide prop erties, 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 w ith this ranking. Combinations of triazoles with the active ingredient s kresoxim-methyl and chlorothalonil, which are known to inhibit spore germination, significantly improved the longevity of the remaining gr een leaf area in comparison with disease-free treatments with triazole s alone. The results obtained under glasshouse conditions were compare d with field studies on S. tritici development after treatments with t ebuconazole to place the results in context. The comparison of the ass essment parameter PYC and NEC between glasshouse and field trial showe d that curative and protectant fungicide properties based on microscop ic assessments of PYC in the glasshouse correlated well with results f rom field trials.