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Plain Language Summary: Poa annua is a troublesome weed in turfgrass areas such as golf courses, athletic fields, lawns, and sod farms. Controlling P. annua is made more difficult by the growing problem of herbicide resistance, the inherited ability of plants to survive herbicide applications that would normally be lethal. Researchers from 13 academic institutions collected 866 P. annua populations from different states and turfgrass systems to better understand the extent of this problem. Collections were divided and treated with four herbicides and one plant growth regulator. Plants were categorized as “susceptible” or “suspected resistant” based on their response to treatments. Suspected resistance (to at least one or more treatments) was observed in 16.8% of P. annua collections. Herbicide resistance in P. annua is a problem spanning different geographies and management practices. Therefore, coordinated research is needed to explore the scope and nature of the problem in a systematic way. [ABSTRACT FROM AUTHOR]

Take‐all root rot (TARR) is a detrimental disease of ultradwarf bermudagrass (Cynodon dactylon × Cynodon transvaalensis; UDB) putting greens frequently diagnosed where warm‐season grasses are grown. Since this disease is largely aggregated and variable under field conditions, field research is difficult and often yields inconsistent results. Multiple pathogens have only recently been associated with this disease, so practical management solutions such as fungicide efficacy and fungicide application timing have not been thoroughly investigated. Therefore, the objectives of this research were to determine the influence of fungicide selection and fungicide application timing on take‐all root rot management under field and greenhouse conditions. In general, fungicides from the quinone outside inhibitor and/or demethylation inhibitor chemical classes provided the greatest reduction in take‐all root rot severity. Fungicide applications that were made when soil temperatures were between 77–86°F provided the greatest disease suppression. The in vivo greenhouse method developed in this research proved to be an efficient and consistent method to evaluate management practices such as fungicide efficacy on take‐all root rot. This research improves our understanding of fungicide efficacy and fungicide application timing for take‐all root rot management on ultradwarf bermudagrass. Core Ideas: Fungicides from the QoI and/or DMI chemical class provided the greatest reduction in take‐all root rot severity.Apply fungicides when the 5‐day average soil temperature at a 2‐inch depth is approximately 80°F for TARR management.The in vivo screening method developed here is an efficient way to evaluate TARR management parameters. [ABSTRACT FROM AUTHOR]

Turfgrass managers have suspected that runoff-independent movement of herbicides and fertilizers is partially responsible for uneven turfgrass quality in sloped areas. We hypothesized that subsurface lateral solute transport might explain this phenomenon especially in areas with abrupt textural changes between surface and subsurface horizons. A study was conducted to track solute transport using bromide (Br−), a conservative tracer, as a proxy of turfgrass soil inputs. Field data confirmed the subsurface lateral movement of Br− following the soil slope direction, which advanced along the boundary between soil horizons over time. A model based on field data indicated that subsurface lateral movement is a mechanism that can transport fertilizers and herbicides away from the application area after they have been incorporated within the soil, and those solutes could accumulate and resurface downslope. Our results demonstrate that subsurface lateral transport of solutes, commonly ignored in risk assessment, can be an important process for off-target movement of fertilizers and pesticides within soils and turfgrass systems in sloped urban and recreational landscapes. [ABSTRACT FROM AUTHOR]

Constant supply of biomass from the field is limited by the seasonality of production of warm‐season grasses in the transition U.S. region. Delaying harvest after occurrence of freeze may be an alternative to extend the biomass supply period of switchgrass (Panicum virgatum L.) in North Carolina. The objectives of this study were to evaluate the effects of harvest frequency (HF) and harvest timing at the end of the growing season (HT) on switchgrass biomass yield, nutrient (N, P, and K) removal, and dry matter (DM) and ash concentrations. Treatments were the factorial combination of two HF (clipped once [1X] or twice [2X] per season) and three HT (before freeze in October, after first freeze in November, and late winter in February). Delaying harvest after occurrence of freeze did not affect total annual biomass yield for the 2X treatment (average of 15.5 Mg ha−1), whereas for 1X yield declined from 14.4 to 10.1 Mg ha−1 when harvest was delayed from October to February. Ash concentration declined from 29 g kg−1 in October to 14 g kg−1 in February. The DM concentration level reached in February was lowest (893 g kg−1) and it would be considered safe for storage of biomass. Nutrient removal was consistently greater for 2X than 1X (ranging from 43 to 137, 3.6 to 25.1, and 54 to 213 kg ha−1 for N, P, K, respectively). Delaying harvest of switchgrass after a freeze event is feasible when clipping twice a year to extend the window of biomass supply. Core Ideas: Clipping twice per year allows delay of biomass harvest from October to February with no total annual yield loss.Dry matter and ash concentrations were not different between one‐ and two‐time harvests in November and February.The dry matter concentration level reached in February would be safe for storage of the biomass.Nitrogen, P, and K removals were greater for two‐ vs. one‐time clippings. [ABSTRACT FROM AUTHOR]