Full TGIF Record # 63280
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Publication Type:
i
Report
Author(s):Vincelli, P.; Williams, D. W.
Author Affiliation:Departments of Plant Pathology and Agronomy, University of Kentucky, Lexington, KY
Title:Timing of heritage 50WG fungicide for control of gray leaf spot of perennial ryegrass, 1998
Source:Fungicide and Nematicide Tests. Vol. 54, 1999, p. 526.
Publishing Information:St. Paul, MN: American Phytopathological Society
# of Pages:1
Keywords:TIC Keywords: Lolium perenne; Gray leaf spot; Pyricularia grisea; Fungicide evaluation; Disease control; Application timing; Azoxystrobin; Application rates; Disease severity
Abstract/Contents:"The test was conducted on sward exposed to natural inoculum at Griffin Gate Golf Course in Lexington, KY. The fairway was composed principally of perennial ryegrass blend seeded in Sep 95 and overseeded annually. It was maintained at a 0.88-in. mowing height, irrigated as needed, and fertilized with 2.75 lb N/1000 ft² as urea during the previous autumn and with a total of 0.23 lb N/1000 ft₂ as soluble fertilizer applied over four applications during the period Jun-Aug 98. Plots measured 4 ft x 4 ft with 2-ft border and were arranged in a randomized complete block design with four replications. The treatments were designed to learn more about optimizing preventive use of fungicides for controlling gray leaf spot. Sprays were applied on the dates noted below using the CO₂-powered hand-held sprayer fitted with Sray Systems 8003E flat fan nozzles delivering 2.5 gal/1000 ft². Estimates of percent plot surface affected by gray leaf spot were obtained by visual assessment. All data were analyzed using ANOVA and the Duncan's Mutiple Range Test (P=0.05). Weather conditions were generally seasonable prior to and during much of the test, although it may be significant that daily low temperatures were above-normal for much of the summer. Weather in Sep was unusually hot and dry. The disease first appeared at extremely low levels on 27 Jun in a nearby fairway where disease pressure had historically been high. The superintendent found a single, twisted leaf blade with a bluish-gray leaf lesion; the pathogen was confirmed microscopically from that sample. Disease pressure reamined low until after the first week of Aug; the disease severity in unsprayed plots was was 2% and 9% on 3 Aug and 7 Aug, respectively. Disease pressure was high through the rest of Aug and Sep. Intrablock variability was high, as reflected in high coefficients of variation. Nevertheless, it was clear that a single application of Heritage 50WG at 0.4 oz applied on 5 Aug (less than one week before rapid disease progress) provided acceptable control for six weeks during highly disease-conducive weather. Applications of Heritage 50WG twice at 0.2 oz on 21 Jul and 11 Aug resulted in unacceptable levels of disease in mid- to late-Sep. Research needs to continue on optimal rates and timing of fungicides for control of this emerging disease of perennial ryegrass."
Language:English
References:0
Note:Tables
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Vincelli, P., and D. W. Williams. 1999. Timing of heritage 50WG fungicide for control of gray leaf spot of perennial ryegrass, 1998. Fungicide Nematicide Tests. 54:p. 526.
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