Abstract
AbstractThe disease Rhizoctonia leaf and sheath spot (RLSS), caused by Rhizoctonia zeae Voorhees, is problematic in ultradwarf bermudagrass (UDBG) [Cynodon dactylon (L.) Pers. × C. transvaalensis (Burtt‐Davy)] putting greens. Typically, RLSS symptoms are most severe in late summer and appear as frog‐eye patches 10 to 40 cm in diameter. In UDBG, RLSS is often called “mini‐ring” because of the small brown rings that are produced when symptoms are prominent. The effect of N source and N rate on RLSS severity was investigated in 2016 and 2017. Nitrogen sources, ammonium sulfate (AMS) [(NH4)2SO4] and urea (CH4N2O) were applied weekly during the growing season at rates of 4.9, 9.8, and 14.7 kg N ha−1. The study was conducted on ‘P18’ (MiniVerde) and ‘TifEagle’ UDBG cultivars maintained as research putting greens at the Clemson University Pee Dee Research and Education Center in Florence, SC. For both cultivars and in both years, urea decreased RLSS severity when compared to AMS. In November of 2016, RLSS severity increased with increasing rates of AMS; however, a rate response was not evident in 2017. In November of 2016 and 2017, RLSS severity was 25 and 30% when AMS was applied at 14.7 kg N ha−1 wk−1 verses 3 and 1% for UDBG receiving applications of urea at that same rate. These studies demonstrate that utilizing urea as an N source, rather than AMS, is an effective strategy to manage RLSS in UDBG.
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