| A series of experiments were carried out in laboratory, glasshouse and field with the aims of determination of suitable fungicides and their application rates for control seed- and soil-borne fungi by treating turfgrass seed so that turfgrass establishment could be improved. The seeds used hi the experiments included perennial ryegrass (Lolium perenne), tall fescue (Festuca arundinaced) and bluegrass (Poa pratensis), three cultivars of each species, which were obtained from Trifolium Co., Denmark; Barenbrug Co., The Netherlands and American International Seed Company.The results obtained from the laboratory trials showed that, the seed germination percentage of perennial ryegrass, tall fescue and bluegrass obtained from filter paper and field soil were 96.25%, 87.83%, 89.25%, and 88.67%, 74.67%, 23.33%, respectively. The corresponding percentage frequency of fungal isolation were 1.92%, 6.17%, 3.17% and 35.67%, 36.00%, 36.33%, respectively. Seed germination percentage was much higher and the fungal isolation rate was much lower on filter paper than those on the field soil (PO.05). The effects of six fungicides including thiram, thiophanate-methyl, triadimefon, chlorothalonil, metalaxyl and copper hydroxide on mycelial growth of 12 fungi isolated were evaluated. The fungi tested were Alternaria altemata, Drechslera poae, Drechslera sp., Fusarium culmorum, Fusarium oxysporum, Fusarium solani, Fusarium sp., Gliocladium roseum, Phoma sp., Pythium sp., and two types of sterile mycelium. Thiram was most effective which was followed bythiophanate-methyl and triadimefon. Those three fungicides were then used to treat seeds of the nine turfgrass cultivars at various rates. Based on seed germination and seedling growth the appropriate rates for each fungicide-cultivar combination were determined. They were thiram at 5g a.i./kg seed for all cultivars tested, thiophanate-methyl at 5g a.i./kg seed for perennial ryegrass, 4g a.i./kg seed tall fescue, and 3g a.i./kg seed for bluegrass, whereas the proper rate of triadimefon for the turfgrass species listed above was 0.4g a.i./kg seed, 0.3g a.i./kg seed, 0.3g a.i./kg seed, respectively.Seeds of nine turfgrass cultivars were treated singly by one of the three fungicides selected at the rate determined previously and the treated seeds were then sown into pots containing field soil. The effects of seed treatment on seed emergence and seedling dry weight varied with the combination of cultivar and fungicide. Thiram treatment significantly increased seed germination of Premier perennial ryegrass and Platini bluegrass by up to 80.6% and 45.2% respectively, 13-17d after sown. Compared to the untreated control, triadimefon seed treatment increased seedling emergence of tall fescue by up to 41.3%~166.7%. Thiram, thiophanate-methyl or triadimefon increased shoot dry weight per pot of Taya perennial ryegrass by 47.2%, 29.5% and 34.7%, respectively, and Thiram or thiophanate-methyl increased the root dry weight per pot of the same cultivar by 67.6% and 97.1%, respectively. Thiram or triadimefon treatment increased shoot dry weight of Gator 13 ryegrass by 32.1% and 29.6%, respectively. Thiophanate-methyl treatment gave the increases of Platini bluegrass root and shoot dry weight per pot up to 230% and 100%. Similar responses to fungicide seed treatments were found on root and shoot dry weight per seedling of all turfgrasses cultivars tested.The results of field experiment showed that thiram seed treatment increased emergence of Premier and Gatorll perennial ryegrass by 13.3%and 33.5%, respectively, while the triadimefon treatment improved the field emergence of those cultivars by 10.8% and 33.5%, respectively. Thiophanate-methyl or thiram increased emergence rate of Barlexas and Houndog-5 tall fescue by 60.5%, 44.8% and 35.9%, 47.5%, respectively. Triadimefon increased seed emergence of Baron and Ronde bluegrass by 40.2% and 47.5%, respectively. Fungicide seed treatments improved biomass of turfgrass tested in different extent. Root and shoot dry weight per pot of...
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