Golf Course Management

MAR 2015

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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94 GOLF COURSE MANAGEMENT 03.15 Evaluating organic amendments for controlling large patch on zoysia Xiaowei Pan Xi Xiong, Ph.D. Michael D. Richardson, Ph.D. James T. English, Ph.D. Shiping Deng, Ph.D. Zoysiagrass (Zoysia japonica Steud.) is one of the most important warm-season grasses. In the transition zone where winter-kill is a concern, zoysiagrass is the dominant grass species managed on golf course fairways and tees. Zoysiagrass has relatively few disease problems except large patch (R izoctonia so - lani AG-2-2 LP), which can be a serious prob- lem if left untreated. Soil organic amendments may provide an alternative strategy for large patch control and potentially reduce dependence on the use of conventional fungicides. It is hypothesized that incorporation of organic amendments en - hances soil microbial populations and/or activ- ity, which adversely affects plant pathogens via antagonism, parasitism or competition. Previous research conducted at the Uni - versity of Missouri demonstrated that a plant-based material, mustard seed meal, can suppress and kill R. solani under laboratory conditions. Field studies showed that applying mustard seed meal in a mixture with sand as a topdressing material following aeration can sig - nifcantly minimize injury to turfgrass plants. In addition, observations from golf course su - perintendents in Missouri and Arkansas indi- cate that animal waste-based organic fertilizers have reduced large patch occurrence and sever - ity. Therefore, the objectives of this study were to evaluate the effects of organic amendments on soil properties and their infuences on large patch occurrence. Field plots were inoculated with R. solani in fall 2012 on zoysiagrass maintained under fairway conditions in Missouri and Arkansas. Application methods included topdressing only or core aerifcation followed by topdress - ing. Organic amendments included mustard seed meal, Back to Nature chicken manure and Milorganite fertilizer at 1,340 pounds/ acre (1,501.94 kilograms/hectare), in addition to UMAXX (urea fertilizer) at 143 pounds/ acre (160.28 kilograms/hectare), Heritage fungicide (azoxystrobin, Syngenta) at 0.4 fuid ounce/1,000 square feet (0.127 milliliters/ square meter), and an untreated control. All organic amendments and synthetic fertilizer provide 1.5 pound nitrogen/1,000 square feet (7.32 grams/square meter) per application. Treatments were applied once in spring and fall in 2013 and 2014. Evaluations included biweekly assess - ments of turfgrass quality, phytotoxicity and large patch cover. Soil physical and chemical properties and soil microbial characteristics were determined before and one year after the initial treatment applications and will also be analyzed in spring 2015, two years after the initial applications. To simplify the discus - sion, only selected results from the Missouri site will be included in this article. Turf injury was found only in plots treated with mustard seed meal at one week after treatment following each application except the spring 2014 application. Topdressing fol - lowing aeration application method reduced mustard seed meal phytotoxicity compared to the topdressing-only method for up to 40% improvement. Regardless of application method, the affected turf completely recov - ered by two weeks after treatment. Large patch was signifcantly reduced in plots receiving chicken manure and the fun - gicide, compared to the untreated control over the two seasons. This trend was similar to the ratio of gram-positive to gram-negative bacte - ria in the soil. Earlier research reported that some gram-negative bacteria, like Pseudomo - nas fuorescens, can suppress many root fungi including R. solani. Studies in both Missouri and Arkansas are ongoing to corroborate cor - relations we observed from this feld study. In summary, repeat applications of organic amendments, such as chicken manure, appear promising for suppressing large patch under feld conditions. Organic amendments dem - onstrate effects on soil microbial populations, and shifts in microbial populations may con - tribute to large patch control. Xiaowei Pan is a graduate student, Xi Xiong (xiongx@mis- is an assistant professor and James T. English is a professor in the department of plant sciences at the University of Missouri, Columbia; Michael D. Richardson is a professor in the department of horticulture at the Uni - versity of Arkansas, Fayetteville; and Shiping Deng is a professor in the department of plant and soil sciences at Oklahoma State University, Stillwater. (Report) Large patch outbreak on a zoysiagrass (Zoysia japonica) fairway, Columbia, Mo. Photo was taken on May 27, 2010. Photo by Xi Xiong

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