Pythium aphanidermatum, P. arrhenomanes and P. volutum are causal agents of damping-off in creeping bentgrass (Agrostis stolonifera L.) in Japan. The optimum temperatures for hyphal growth of the three species were 35ºC, 30ºC, and 25ºC, respectively. We inoculated seedlings of grasses, cereals, and vegetables with the Pythium species at 23ºC and 32ºC in post-emergence tests. P. arrhenomanes showed the highest pathogenicity against seedlings of grasses, cereals, and allium, with stonger effects at 32ºC than 23ºC. P. volutum caused more severe symptoms in grasses at 23ºC than 32ºC. Only P. aphanidermatum caused damping-off at 32ºC in alfalfa, a Fabaceae species. In summary, the three Pythium species showed different temperature optima for growth and disease development, having different host ranges.
From a morphological standpoint, we divided vine of Kudzu into two types (climbing vine and creeping vine) and measured their diameters at 4 habitats in Tochigi prefecture, Japan. Moreover, the number of plant species climbed by the weed and the diameters of their stems were measured at the same habitats as Kudzu. The results obtained from the present study were summarized as follows. Climbing vines were significantly thin as compared to those of creeping vines. And 17 plant species climbed by Kudzu were observed in 4 habitats, and their diameters were ranging from 1.0 mm (Setaria glauca) to 9.2 mm (Bidens pilosa). These results suggest that morphological differentiation of the vine (climbing type or creeping type) is greatly related to the diameter of the vine, and Kudzu climbs various plants regardless of their size and species.