C. jacksonii sp. nov. formerly S. homoeocarpa F.T. Bennett, the causal agent of DS, is the most widespread pathogen in turfgrass systems (Bishop et al., 2008; Salgado-Salazar et al., 2018). DS affects both cool- and warm-season grasses, during a wide range of environmental conditions. Small tan lesions surrounded by a darker band and often presenting an hourglass appearance in circular patches 10 to 40 mm, and white mycelium characterize DS. Once blighted, turf areas often become necrotic and bare, often susceptible to weed invasion. During favorable conditions, spots may coalesce to form larger irregular shaped patches (Salgado-Salazar et al., 2018; Smiley et al., 2005). Management of DS includes regulating surface moisture levels, proper nitrogen management, and both preventive and curative applications of fungicides. Increased pressure to manage turf in a more ecologically friendly, greener manner has reinvigorated the search for suitable biological fungicides. Aiding the drive are costs associated with synthetic fungicides and perceived risks to humans and the environment.
As an alternative to synthetic products, bacterial and fungal species are being evaluated for their ability to suppress DS. BCAs offer both advantages and disadvantages to turf managers. Potential biological species for use are native to most soils, and thus pose low toxicity risk to humans and wildlife. Synthetic products are subject to degradation, where active parent products are degraded into secondary metabolites that may pose certain risks (Harman, 2006). However, currently available BCAs typically show reduced acute efficacy and residual control. Application timing becomes much more critical, especially during high disease pressure conditions. Packaging and shelf life issues also pose challenges. Most of these products contain living organisms, requiring short-term storage under specific conditions (Kim et al., 1997). In this study, the goal was to investigate if quarter low label rates of the synthetic fungicides CL and AzP in combination with BCAs could provide similar control as full label rates of the synthetic fungicides.
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