Investigations of damage effects and control methods of two new phytopathogens of soybeans in Austria: Colletotrichum dematium (Pers.) Grove f. truncatum (Schwein.) Andrus & W. D. Moore and Diaporthe phaseolorum (Cooke & Ellis) Sacc.

摘要

Soybean varieties were examined for field infestation with C. dematium and D. phaseolorum in three different climatic regions of Austria. These phytopathogens have not been recorded from Austria before. Furthermore, investigations on yield, varietalsensitivity and mycological contamination of the harvested crop were conducted after treatment with fungicides whose active ingredients belong to the strobilurin derivative, triazole, dithiocarbamat-phenylamide and imidazol groups. The varieties Ceresia, Essor, Labrador and Quito displayed resistant qualities toward C. dematium. Varieties of the ripening class 000 generally showed higher susceptibility to C. phaseolorum. The varieties Ceresia, Quito, Apache and Essor showed less susceptibility to D. phaseolorum. In the years 1995-1999 fungicide treatments significantly reduced infection on the average by 20-40 percent (Newman-Keuls Multiple Comparison test, (#alpha# = 0.05). Folicur (250 g/l tebuconazole), with 43 percent efficacy gave the best protection against C. dematium. Against D. phaseolorum fungicides from all groups of active substances were within the range of 30 percent efficacy. On the average fungicides treatments increased grain yields by 5 to 10 percent. In years with particularly highdisease pressure yield increases of up to 20 percent could be achieved. Besides D. phaseolorum and C. dematium mycological investigations of the harvested crop detected a number of other seed-borne diseases, e.g. Alternaria ssp., Fusarium ssp., Phoma exigua, Rhizoctonia solani Pseudomonas glycinea and Xanthomonas phaseoli. Infestation of the harvested seeds with D. phaseolorum lay under or around 5 percent at two of the three locations. Approximate 50 percent of the grains were infected with D. phaseolorum at one location in the humid area. In this case a strobilurin derivative gave the best protection with 50 percent efficacy, whereas fungicides with other active ingredients showed about 25 percent efficacy. Infestation of the harvested crop with C.dematium was below 5 percent at all three locations. With respect to leaf, stem and pod infestation by both diseases, grain samples from the arid area were generally substantially healthier than those from the humid area: dry region (experimental stationFuchsenbigl) 50 percent free of infestation, humid region (experimental stations Petzenkirchen and Reichersberg) 5 percent free of infestation.