Plant growth regulators (PGRs) are commonly applied to ultradwarf hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] putting greens during the growing season. Trinexapac‐ethyl (TE) and prohexadione‐Ca (PH) are PGRs that inhibit gibberellic acid biosynthesis and are used to reduce clipping yield and improve turfgrass visual quality. Growing degree day (GDD) models have optimized the timing of PGR reapplications to creeping bentgrass (Agrostis stolonifera L.) putting greens, but no information is available regarding proper PGR reapplication timing on bermudagrass putting greens. The objective of this research was to develop a GDD model to determine optimal TE and PH application frequencies on bermudagrass putting greens. Field research was conducted on three ultradwarf cultivars at separate locations in the southeastern United States: ‘MiniVerde’ in Knoxville, TN, ‘Champion’ in Durham, NC, and ‘TifEagle’ in Starkville, MS. Peak yield suppression was 49 to 65% after TE application at 0.034 kg a.i. ha−1 and 50 to 54% after 0.154 kg PH ha−1. Peak suppression occurred later for TE (166–177 GDD calculated using 10°C as the base temperature [GDD10C]) than for PH (92–97 GDD10C), which resulted in an estimated PGR reapplication interval of 216 to 230 for TE and 120 to 126 GDD10C for PH. Enhanced clipping yield and rebound did not follow clipping yield suppression. The use of a GDD model to schedule PGR applications on bermudagrass putting greens has the potential to maximize PGR benefits; however, season‐long implementation of this GDD model needs comparison with current PGR programs used on ultradwarf putting surfaces.

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Spring dead spot (SDS) of bermudagrass (Cynodon dactylon) is primarily caused by Ophiosphaerella herpotricha and Ophiosphaerella korrae in North America. These two species respond differently to numerous management practices, grow optimally at different soil pH ranges, and differ in aggressiveness. Understanding the Ophiosphaerella species distribution in regions where SDS occurs will allow turfgrass managers to tailor their management practices toward the predominant species present. A survey was conducted in the Mid-Atlantic United States in which one to 14 samples of bermudagrass expressing SDS symptoms were taken from 51 athletic fields, golf courses, or sod farms across Delaware, Maryland, North Carolina, and Virginia. DNA was isolated from necrotic root and stolon tissue, amplified using species-specific primers, and detected in a real-time PCR assay. At least one isolate of O. herpotricha was recovered from 76% of the locations and O. korrae was recovered from 73% of the locations. Ophiosphaerella herpotricha was amplified from 55% of the samples while O. korrae was amplified from 37% of the samples. There were distinct regions in the Mid-Atlantic in which either O. herpotricha or O. korrae was predominant. Ophiosphaerella herpotricha was predominant in western Virginia, central North Carolina as well as Delaware and eastern Maryland. However, O. korrae was predominant in central Maryland and Virginia as well as eastern Virginia and North Carolina. Ophiosphaerella herpotricha was isolated from certain cultivars more frequently than O. korrae and vice versa. These survey results elucidate the geographic distribution of O. herpotricha and O. korrae throughout the Mid-Atlantic United States.

Dollar spot (Clarireedia spp.) is a damaging turfgrass disease. Ferrous sulfate (FeSO 4 ) suppresses dollar spot with little risk of resistance. Optimizing FeSO 4 applications is crucial for adequate dollar spot suppression. Supplementing FeSO 4 applications with chlorothalonil fungicide could also increase efficacy against dollar spot and longevity of disease suppression. Four experiments were conducted to determine the 1) optimal water carrier volume for FeSO 4 , 2) proper nozzle selection for FeSO 4 applications, 3) most efficacious rate combination of FeSO 4 and chlorothalonil, and 4) longevity of chlorothalonil efficacy when applied in conjunction with FeSO 4 for dollar spot suppression on creeping bentgrass (Agrostis stolonifera L.). These studies were conducted on either putting greens mown at 3.2 to 6.4 mm or fairways mown at 16.5 mm. The following carrier volumes were tested in Experiment 1: 281, 421, 842 and 1684 L ha -1 . For Experiment 2, Turbo FloodJet (TF), Turbo TeeJet Induction (TTI), Air Induction Turbo TwinJet (AITTJ), and Extended Range Flat Fan (XRFF) nozzles were used to determine optimal nozzle type. In Experiment 3, chlorothalonil was applied at 0, 2.28, 4.57, 6.86 and 9.16 kg a.i. ha -1 with or without 48.8 kg ha -1 of FeSO 4 . In Experiment 4, 48.8 kg ha -1 of FeSO 4 was applied biweekly and chlorothalonil was curatively applied at 8.2 kg a.i. ha -1 when infection centers per plot reached 30. Water carrier volume had no effect on dollar spot suppression, the AITTJ and XRFF nozzles provided the greatest disease suppression and turf quality, FeSO 4 reduced effective chlorothalonil rates by up to 68.5% and FeSO 4 increased longevity of chlorothalonil efficacy.