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Nitrogen and Iron Sulfate Affect Microdochium Patch Severity and Turf Quality on Annual Bluegrass Putting Greens

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Nitrogen and Iron Sulfate Affect Microdochium Patch Severity and Turf Quality on Annual Bluegrass Putting Greens Published October 26, 2016 RESEARCH Nitrogen and Iron Sulfate Affect Microdochium Patch Severity and Turf Quality on Annual Bluegrass Putting Greens Clint M. Mattox,* Alec R. Kowalewski, Brian W. McDonald, John G. Lambrinos, Brian L. Daviscourt, and Jay W. Pscheidt C.M. Mattox, A.R. Kowalewski, B.W. McDonald, J.G. Lambrinos, ABSTRACT and B.L. Daviscourt, Dep. of Horticulture, 4017 Agricultural and Microdochium patch is an important turfgrass Life Sciences Building, Oregon State Univ., Corvallis, OR 97331; disease in cool-humid regions and is caused J.W. Pscheidt Dep. of Botany and Plant Pathology, 1089 Cordley by the pathogen Microdochium nivale (Fries) Hall, Oregon State Univ., Corvallis, OR 97331. Received 24 Feb. Samuels & Hallett. Control of the pathogen is 2016. Accepted 28 July 2016. *Corresponding author (Clint.Mattox@ necessary to provide acceptable putting-green- oregonstate.edu). Assigned to Associate Editor Douglas Soldat. quality turf, and fungicide applications are the Abbreviations: AUDPC, area under disease control progress curve. predominant method of control. Increasing pesticide restrictions have generated interest in alternative management techniques of Micro- icrodochium patch is a turfgrass disease caused by the dochium patch. This research evaluated the Mfungal pathogen Microdochium nivale (Fries) Samuels & Hal- effects of three nitrogen and five iron sulfate lett and is most active in the field when temperatures are between rates on Microdochium patch development on 8 and 17°C and when there are more than 20 h of ³90% humid- a trafficked, sand-based, annual bluegrass Poa( ity (Dwyer, 2004). These conditions are common in the Pacific annua L.) putting green in Corvallis, OR for over Northwest and northern Europe, where Microdochium patch is 2 yr in the absence of fungicides. Data included one of the most prominent turfgrass diseases (Vargas, 2005). Fungi- turf quality, area under disease progress curve, cide applications are currently the predominant method of control and soil test results of saturated paste extract pH, cation extractable sulfate, and DTPA-sor- for Microdochium patch; however, increasing pesticide restrictions bitol extractable iron. This research provided in North America and Europe (Ministère de l’agriculture et de la evidence that low rates of urea (4.88 kg N ha−1) pêche, 2006; Christie, 2010) are causing turfgrass managers to look applied every 2 wk did not lead to an increase for alternative ways of managing this disease. in Microdochium patch severity and that iron Microdochium patch severity has often been linked with sulfate applications decreased Microdochium turfgrass nutrition. High levels of nitrogen (N) fertility have patch on annual bluegrass putting greens. been associated with an increase in susceptibility of turfgrass to Despite the disease suppression observed, no Microdochium patch, referring to N’s impact on leaf succulence, treatment received a turf-quality rating consid- although no guidelines are provided as to how much constitutes a ered acceptable. Low turf-quality ratings where high level (Smiley et al., 2005). Early studies showed that Micro- disease development was low were attributed dochium patch severity increased as a result of higher annual N to turfgrass thinning or blackening of the shoots applications on both annual bluegrass (Poa annua L.) and colo- resulting from iron sulfate applications. Soil tests provided evidence that the highest iron sulfate nial bentgrass (Agrostis tenuis Sibth.) (Sports Turf Bulletin, 1956; level used in this study (97.65 kg ha−1) applied Brauen et al., 1975). However, there is little, if any, peer reviewed every 2 wk would likely lead to a lower soil pH research investigating how low rates of N (e.g., 4.88 and 9.76 kg N −1 −1 and an increase in soil sulfate levels. ha 2 wk ), applied during the late fall and winter periods, affect Published in Crop Sci. 57:1–8 (2017). doi: 10.2135/cropsci2016.02.0123 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. CROP SCIENCE, VOL. 57, 2017 WWW.CROPS.ORG 1 Apr. 2015. All treatments were applied with a CO –pressurized Microdochium patch activity and turfgrass recuperation 2 resulting from golfer traffic in the absence of fungicides. backpack sprayer with a four-nozzle (25.4 cm of nozzle spacing) handheld boom equipped with four XR80015 nozzles using a Soil pH is often reported to have an effect on Micro- pressure of 280 kPa at the boom. Carrier volume was 814 L ha−1 dochium patch severity with higher pH considered and walking speed was calibrated with a metronome. To simulate conducive to disease (Smith, 1958; Couch, 1995; Smiley golf conditions similar to those of a municipal course in Corvallis, et al., 2005). A study on colonial bentgrass in Puyallup, OR, golfer traffic representing 76 rounds of golf per day was per- WA, showed that 224 kg of sulfur ha−1 annually resulted formed by walking over the plots using golf shoes, following the in complete control of Microdochium patch (Brauen et protocol set out by Hathaway and Nikolai (2005). al., 1975). Unlike sulfur (S), which requires microorgan- isms for oxidation to occur (and is therefore temperature Turfgrass Maintenance −1 dependent) (McCarty et al., 2003), iron sulfate (FeSO4) The green was mowed once wk in November through March reacts readily with water to release hydrogen ions, result- and five times wk−1 for the rest of the year, at a mowing height ing in a reduction of soil pH (Carrow et al., 2001). The use of 3.8 mm with clippings removed. Preceding the first year of the trial, 234 kg N ha−1 was applied from April to the begin- of FeSO4 to manage Microdochium patch is a common practice in Europe (Baldwin, 1989; Mabbett, 2014; Pitch- ning of the trial using a quick release compound fertilizer care, 2015) and has also been shown to reduce dollar containing 23.7% urea N and 4.3% nitrate N (28 N–2.2 P–15 spot (Sclerotinia homeocarpa Bennett) severity in Virginia K) (Andersons 28–5–18, Maumee, OH) to establish the green. The August applications of this fertilizer consisted of 9.8 kg N (Reams, 2013). With the exception of a 1-yr study in the ha−1, applied on 2, 16, and 29 Aug. 2013. Urea was applied on United Kingdom on a mixed stand of turfgrass where a 5 and 20 Sept. 2013 at a rate of 9.8 kg N ha−1. Between the two decrease in Microdochium patch severity was observed trial years, 80 kg N ha−1 was used to recover the green from the due to FeSO4 additions (Oostendorp, 2012), little research damage of the first year. The same Andersons 28–5–18 fertil- −1 exists that quantifies the effects of FeSO4 applications on izer was applied at a rate of 9.8 kg N ha on 8 and 22 Aug. the severity of Microdochium patch. 2014, as well as on 5 Sept. 2014. A 9.8-kg N ha−1 application of The objective of this study was to quantify the effects urea was made on 19 September. Sand topdressing was applied at a rate of 2.7 L m−2 every 2 wk from 5 July to 5 Sept. 2013, of FeSO4 and urea application rates on the severity of Microdochium patch on an annual bluegrass putting and again from 3 July to 2 Sept. 2014. Hollow-tine aerifica- green, as well as turf quality affected by simulated golfer tion using 13-mm diameter tines on 5.1- by 5.1-cm spacing traffic in the absence of fungicide applications. at a 76-mm depth was performed on 18 Sept. 2013, and again on 19 June and 16 Sept. 2014. No fungicide treatments were applied throughout the study. Fungicides were applied as a pro- MatERIALS AND METHODS phylactic against Anthracnose (Colletotrichum cereale Manns) and Experimental Design dollar spot in each summer before the trials started. During the The experiment was conducted at the Oregon State Univer- trial period, no irrigation was applied due to the cool-humid sity Lewis–Brown Horticulture Farm in Corvallis, OR, on a conditions in the Willamette Valley. During the summer, irri- putting green constructed by placing 15 cm of USGA-recom- gation was applied using well water with a pH of 6.3. Irrigation mended particle-size sand (USGA, 2004) directly on the native was set to replace 50% of the evapotranspiration every day, and McBee silty clay loam (fine-silty, mixed, superactive, mesic the green was hand watered to avoid drought stress; peak rates Aquic Cumulic Haploxerolls) (UC Davis, 2015). Annual blue- during summer heat stress resulted in 2.4 cm of water being grass was established by using aerification cores from an annual applied per week. bluegrass putting green with USGA sand at a local country club in Corvallis, OR. The experimental design was a 3- by 5-fac- Response Variables torial treatment structure arranged in a randomized complete Response variables included area under disease progress curve block design with four replications. The trial was repeated over (AUDPC), turf quality, saturated paste extract pH, DTPA-sor- 2 yr. Individual plots were 1.5 m2, and the total experimental bitol extractable Fe, and cation extractable sulfate levels. area was 90 m2. Factors included three urea (46 N–0 P–0 K) Area under disease progress curve data were calculated −1 rates (0.0, 4.88, and 9.76 kg N ha ) and five FeSO4 heptahy- using disease severity data quantified by stratified sampling that drate (11.5% S and 20.1% Fe) rates (0.0, 12.21, 24.41, 48.82, were collected monthly after the initial data collection (26 Sept. and 97.65 kg product ha−1). Urea rates of 4.88 and 9.76 kg N 2013 and 22 Sept.
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