| Mile-a-minute weed (MAM) (Polygonum perfoliatum L.) is an invasive plant introduced from eastern Asia in 1930s and subsequently spread to nine states and the District of Columbia. Natural enemy surveys conducted in the eastern US found no effective biological control agent for MAM.; This research focused on determining the phenology of MAM in southern China and developing seed germination tests in both the northeastern US (temperate region) and subtropical southeastern China. Surveys and collections were conducted in selected areas of China to determine fungal associates of MAM and evaluate the potential of selected fungal associates as biological control agents.; The phenology study suggested that MAM was a summer annual plant with a longer life span in warmer climates, such as Guangzhou, in subtropical region in southeastern China, than in temperate regions of northeastern US. A short frost period in November or December kills the plants, but by following January or February, the seeds germinate to produce new plants. The seeds of MAM were capable of germinating with a shorter stratification period, 3--10 weeks to break the dormancy in southeastern China, as compared to plants in temperate regions of northeastern US with a stratification period of 4--19 weeks.; Surveys and collections from 1997 to 2002 produced more than 50 disease samples of MAM collected from 13 locations in six provinces in northeastern, northern, central, and southwestern China. Over 300 fungal isolates were obtained from these samples. A rapid testing for their relative pathogenicity was conducted on detached leaves. There were 44.5% of the fungal isolates having no infection (rating of 0, no lesion); 13.1% having an intermediate infection (rating of 1, lesion < 1cm); and 42.4% having high infection (rating of 2, lesion >= 1 cm).; Significant differences were in the proportion of infection ratings for the various fungal isolates among geographical areas (province and locations). The rankings of proportions of high infection ratings from different provinces were in the following order: Guizhou>Heilongjiang>Shandong>Liaoning and Henan>Beijing.; All selected pathogenic fungal isolates with high infection ratings (rating of 2) from Guizhou and Shandong provinces were Alternaria spp.; those collected from Henan and Liaoning provinces were more diversified, including Colletotrichum spp., Fusarium spp., Phyllosticta sp., Ascochyta sp., Sphaeropsis sp., and Rhizoctonia sp. as well as Alternaria spp.; The results of this study indicate that MAM has its pathogenic fungal associates in its native range in China, and their pathogenicity varies among geographical areas.; A fungal isolate, CQ4R, was isolated from MAM plants with blight symptoms in Beibei District, Chongqing in southwestern China in August 2003. It was identified as Nigrospora sp. Pathogenicity tests and preliminary host range testing were done for CQ4R using a detached leaf assay and whole plants of MAM with some closely related plants at different temperatures and moistures.; Results also indicate that CQ4R can cause quick infection on MAM detached leaves and whole plants, at warm and humid environment and a moderate temperature and moisture. Preliminary host range testing showed no infection on tomato seedlings or P. thunbergii, a close related plant of MAM in Asia. |
