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Abstract
Ten fungous diseases of Bromus species in New Zealand are discussed, of which four are of economic importance on Bromus willdenowii Kunth.
Cercosporella bromivora sp. nov. incites large, irregular-shaped lesions on leaves and stems of eight species of brome. The fungus grows slowly on PDA, and sporulates profusely. Controlled-environment studies indicate that this disease is most severe between 16°C and 20°C.
Colletotrichum graminicola (Ces.) Wils, has been isolated from elongate necrotic streaks on B. willdenowii and inoculated into 10 other bromes. Maximum disease development is between 16°C and 20 °c.
Ustilago bullata Berk, causes head smut in six Bromus species. Field trials have shown many lines of B. willdenowii to be resistant. Five oz per bushel of 50% thiram dusted on smutted seed gave good disease control.
Fusarium nivale (Fr.) Ces. is primarily a pathogen inciting irregular, brown leaf and stem lesions on 19 bromes; however, mild root infection is occasionally induced when fungal spores are introduced to the root zone. The optimum temperature for this disease is around 20°C.
The six fungi mentioned below are of little or no importance on B. willdenowii in this country.
Ramularia pusilla Unger incites eyespot leaf lesions on B. willdenowii and has been inoculated on to 15 other Bromus species and three other grass genera. Temperatures between 20°C and 24°C are optimum for this disease.
Puccinia recondita Rob. ex Desm. does not infect B. willdenowii, but it is reported on 25 other bromes.
Ascochyta sorghi Sacc., Septoria bromi Sacc., and Selenophoma bromigena (Sacc.) Sprague and A. G. Johnson have been isolated from minor leafspots on several bromes. Claviceps purpurea (Fr.) Tul. has been reported only on B. inermis Leyss. and B. mollis L.