| Abstract/Contents: | "Fungicides were evaluated in 2 seperate tests at the Valentine Turfgrass Research Center, University Park, PA, on perennial ryegrass maintained under home lawn/golf course fairway management conditons. The turf was fetilized on 14 Apr with 0.5 lb actual N (NH4NO3)/1000 sq ft. Tersan 1991 at 2.0 oz/ 1000 sq ft was applied on 9 and 27 Jun, and 29 Jul to control large brown patch in the experimental area. Cadminate was applied for the control of red thread on 9 Jun and 29 Jul (0.5 oz/1000 sq ft). Individual treatment plots, 3 ft x 18 ft, were arranged in a randomized complete block design with 3 replications. Fungicides were applied with a CO2 powered, boom sprayer with 8004 Tee Jet nozzles, at 30 psi, in water equivalent to 2 gal/1000 sq ft. Fungicide treatments were applied once in each test. Three days after fungicide application, in the first test, a 3 ft-wide strip across all treatments was ioculated with a 6-isolate pool of P. aphanidermatum grown on autoclaved ryegrain. A second inoculation was made 7 days after treatment, in the manner described above. In the second test, successive inoculations were made at 1, 7, 14, and 24 days after treatment, as above, to evaluate lon-term disease suppression. The 3 ft-wide inoculated strip was covered, following each inoculation, with PVC pipe-framed, tranlucent, plastic covered humidity chambers, containing intermittent mist to maintain a saturated atmosphere and to minimize radiational cooling at night. Chamber ends were open and two 1 minute mists/hr were applied during daylight hours. At night, chambers ends were closed and mist was not applied. After approximately one week incubation, the chambers were removed and the inoculated areas were visually rated at 7 and 17 days in the first test, and , in the second test, at 7,14, 21, and 28 days after treatment, respectively. Data obtained were subjected to analysis of variance and Waller-Duncan K-ratio t test. Data from 7, 21, 28 days post treatment (test 2), and 17 days post treatment (test 1) are presented. Conditions were unfavorable for disease development in the initial inoculation of first test. Since data from this period are critical for complete evaluation of fungicides in our test procedue, it was necessary to undertake the second test to obtain data for the 7 day post treatment interval. Through 17 days following fungicide application, excellent control was obtained with Subdue 2E at 1 and 2 fl oz, Fluid Fungicide II at 0.7 and 1.4 fl oz, and the half-rate mixture of Subdue and Aliette. Subdue 2G-D at 25 oz provided excellent control at 17 and 21 days post treatment, and by 28 days after treatment, although control was not commercially acceptable, disease suppression was significantly different from all other treatments, including the untreated check. This formulation is a large particle granule, and may provide a slow release of metalaxyl over an extended period. This view is further supported by the finding that control at 17 days post treatment was greater than at 7 days." |
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