| Abstract/Contents: | "Twenty cultivars of four species of bentgrass (Agrostis spp.) were established in Maury silt loam on 21 Sep 89 as part of the National Bentgrass Fairways and Tees Evaluation. Three replicated plots (8 X 12 ft) of each variety were arranged in a RCB design. Two fall applications of urea (4.0 lb nitrogen/A) were made in 1990. Temperature and rainfall at the University of Kentucky Spindletop Research Farm were unusually high during Apr and May, tapering to drought conditions by the end of Jun. Plots were maintained at a height of 0.5 inches and were not irrigated during the evaluation period. Susceptiblity to dollar spot (DS) was evaluated by counting DS infection centers on 25 Apr and 27 May. Brown Patch (BP) was evaluated by estimating percent of infected turf on 7 May and 27 June, using the scale in the table below. Number of DS infection centers, BP estimates for each month, percent increase in DS (Apr to May), and percent increase in BP (May to Jun) were analyzed statistically by analysis at variance (GLM, SAS) and Waller-Duncan K-ratio mean separation test at P = 0.05. Disease pressure from both pathogens was high, allowing for evaluation of varietal differences of resistance to both DS and BP. There were significant differences in the number of DS infection centers (Apr and May), the percent BP (May and Jun), and percent increase in BP. Total number of DS infection centers per plot ranged from 24 to 345 in Apr, and 97 to 362 in May. DS was more variable in Apr than in May, and the percent increase across all varieties was not significant. In this evaluation partial resistance (lower disease levels, P = 0.05) to DS was displayed by twelve varieties in Apr and May (Allure, BR 1518, Bardot, Cobra, Egmont, National, Regent, Penneagle, Providence, Tracenta, 88 CBE and 88 CBL). BP was active in May and increased in sixteen cultivars at the Jun rating and decreased in four (Allure, Bardot, BR 1518 and Tracenta). Partial resistance to BP was exhibited by the varieties Carmen, Cobra, Procup, National, Penncross, Penneagle, Providence, Putter, SR 1020, Tamu 881, WVPB 89D15, and 88 CBL in May and Jun. The variety National had the best visual appearance, and exhibited partial resistance to both diseases in these evaluations. Cobra, Penneagle, Providence and 88 CBL also exhibited partial resistance to both diseases. Comparatively high levels of resistance to either dollar spot or brown patch were observed in individual varieties, but no variety displayed a level of resistance to either disease adequate to obviate chemical control. Further research will be needed to determine if chemical control strategies can be integrated with disease resistance to minimize fungicide use for fairways and tees." |
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