A new disease was found on Kentucky bluegrass (Poa pratensis) turf on a golf course in Hokkaido, Japan, from summer through early autumn in 2002 and 2003. Symptoms showed circular patches or rings of brown to tan color ranging from 20 to 40 cm in diameter. Sometimes irregular patches were also found. This disease is characterized by a blackening of roots and rhizomes affected by a disease. Darkly pigmented ectotrophic hyphae and mycelial aggregations were consistently observed on roots and rhizomes. A specific fungus was consistently isolated from roots and rhizomes. Optimal growth rates of the fungus on potato-sucrose agar were between 20 and 25°C. The fungus was found to be pathogenic on Kentucky bluegrass and three other species of cool-season grasses. The fungus was also pathogenic on three species of warm-season grasses. Based on morphological characteristics of pseudothecia, asci and ascospores, the fungus was identified as Ophiosphaerella korrae (J. Walker & A.M. Sm.) Shoemaker & Babcock. We proposed that the name of the new disease on Kentucky bluegrass caused by O. korrae in Japan is ‘necrotic ring spot’ (necrotic ring spotbyo in Japanese) .

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Among the poor growth syndrome of manilagrass (Zoysia matrella), Japanese lawngrass (Z. japonica) and hybrid zoysiagrass (Z. japonica×Z. matrella) turf, that is called ‘shizumi-sho’ in Japanese, we found a new disease in Japan. Symptoms showed circular patches or rings ranging from 10 to 40 cm in diameter. Sometimes irregular patches were also found. This disease is characterized by a blackening of roots and stolons affected by a disease. Darkly pigmented ectotrophic hyphae and mycelial aggregations were consistently observed on roots and stolons. Optimal growth rates on potato-sucrose agar of a fungus which was consistently isolated from roots and stolons were between 20 and 25°C. The fungus was pathogenic on manilagrass, Japanese lawngrass, hybrid bermudagrass (Cynodon dactylon×C. transvaalensis) and four species of cool-season grasses. Pathogenicity of the fungus on manilagrass was higher than that of Phialophora sp. which is known to cause zoysia decline. Based on morphological characteristics of pseudothecia, asci and ascospores, the fungus was identified as Ophiosphaerella korrae (J. Walker & A. M. Sm.) Shoemaker & Babcock. We proposed that the name of the new disease on zoysiagrass caused by O. korrae in Japan is ‘necrotic ring spot’ (necrotic ring spot-byo in Japanese) .

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Two production models, one using a neural network and the other using a multiple regression analysis, were constructed based on data of monthly dry matter production under various climatic conditions for Zoysia japonica. These models were then evaluated for practical use by comparing conformity of estimated data with actual harvest data. Using 105 items of harvest data with Zoysia japonica for three years, these models were compared for the estimation accuracy each other. The results clearly showed that the neural network had a higher coefficient of correlation between estimated data and harvest one. Accordingly, the neural network model showed the better estimation for the productivity.

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The combination effects of 5-aminolevulinic acid (ALA) and the nitrogen fertilizer containing Mg, Fe and other trace elements on the growth of creeping bentgrass (Agrostis palustris Huds. c.v. Penn. A-1, A-2, mix) were studied. The results demonstrated that ALA and the fertilizer showed synergistic and promotive effects on the dry weight and the turf color of creeping bentgrass in a greenhouse during winter. Additionally, there is a possibility that the growth and the turf color of creeping bentgrass were improved by the application of the fertilizer containing ALA during summer. These effects are interaction with ALA and the fertilizer. It was demonstrated that a promotive growth effect of ALA for creeping bentgrass is affected by a plant nutritional conditions.

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