Annual bluegrass (Poa annua L.) is perhaps the most common and problematic weed on creeping bentgrass (Agrostis stolonifera L.) putting greens.  Various field trials have been conducted to investigate the influence of select plant growth regulators (PGRs) and fertility regimes on annual bluegrass (ABG) populations.  Few studies, however, have investigated the interactions among these factors in combination with ferrous sulfate; an increasingly popular ABG management regime for golf course turf.  The objective of this project is to elucidate the interactions of three cultural and chemical management strategies on ABG populations on golf course putting greens.  Four field studies were initiated in the spring of 2010 at the Joseph Valentine Turfgrass Research Center located in University Park, PA.  Trials were conducted on a mature stand of ‘L-93’ creeping bentgrass with approximately 25% ABG when the study was initiated.  The area was mowed six times per week at a height of 2.5 to 3.2 mm.  All trials were exposed to minimum surface disturbance and received no supplemental phosphorous.  Plots measured 0.9 x 1.8 m and were arranged in a randomized complete block design with a factorial treatment structure.  The four studies consisted of either a 2 x 3 or 2 x 3 x 3 factorial with the main factors of nitrogen (N) rates, plant growth regulators, and ferrous sulfate rates. Treatments were initiated on 26 May and applied approximately every 3 weeks throughout the season.  All treatments were applied in 4073 L H₂O/HA.  Seasonal fluctuations in ABG populations were observed during the study. When ABG populations were highest, plots receiving flurprimidol provided the greatest suppression of ABG when compared to all other treatments. Populations of ABG were generally lower in plots receiving low seasonal nitrogen (25 kg N/HA/year) when compared to plots receiving high seasonal nitrogen inputs (107 kg N/HA/year).  Additionally, applications of trinexapac-ethyl to low N plots resulted in a 58% reduction of ABG when compared to plots receiving no PGR.  This result, however, was not observed within plots receiving 107 kg N/HA/year. Although ferrous sulfate (all rates and combinations) had little impact on ABG populations, it was effective at improving turf color. The effects of these cultural and chemical interactions will continue to be assessed to determine any long term positive or negative impacts on species segregation and overall turf quality.