Impact of nitrogen source, fall fertilizers, and preventive fungicides on spring dead spot caused by Ophiosphaerella korrae and O. herpotricha

The effects of N source, fall fertilization, and preventive fungicides were evaluated in bermudagrass [Cynodon dactylon (L.) Pers.] artificially inoculated with Ophiosphaerella korrae and O. herpotricha, the most common spring dead spot (SDS) pathogens in the United States. The source of N applied to bermudagrass from May to August 2006-2008 had a significant effect on SDS symptoms appearing in the spring of 2007-2009. Ammonium sulfate [(NH4)(2)SO4] provided excellent suppression of O. herpotricha but had no effect on O. korrae, which was suppressed instead by calcium nitrate (CaNO3). More research is needed to determine the underlying mechanisms responsible for suppression of SDS with N sources and the potential role of Mn and Ca in development of the disease. Fall applications of K, S, gypsum, or dolomitic lime had no influence on SDS development. Preventive applications of propiconazole, propiconazole + azoxystrobin, tebuconazole, or fenarimol provided effective control of O. herpotricha but failed to provide significant suppression of O. korrae. The differential response of SDS pathogens to fertilization practices and preventive fungicide applications highlight the importance of pathogen identification in development of integrated management programs.

Automated summary

The choice of nitrogen source and fall fertilization have significant impacts on the development of spring dead spot (SDS) in bermudagrass. Different fertilization practices and preventive fungicide applications have varying effects on the SDS pathogens, highlighting the importance of pathogen identification in integrated management programs.