The Poa annua that has invaded these bentgrass greens is most likely and predominantly an annual biotype having generally an open growth habit, appears whitish in color, and is a prolific seedhead producer. The seedhead production from these more annual biotypes is exasperated by management practices (lower mowing heights), and environmental stresses (ex. moisture stress) compared to the more perennial biotypes.

The two photographs provide a nice contrast between the annual and perennial biotypes. Both photographs were taken from the same golf course in the Cincinnati area around the first week in May. The top photograph was taken on a creeping bentgrass green where the annual biotype most likely germinated last fall and established this spring. The bottom photograph is another green on the same golf course that has been predominantly Poa annua for several years. Perennial types of Poa annua produce less seedhead inflorescences.

The good news with these annual types is that they should disappear with the arrival of summer. The downside is that does not help you at the moment. My suggestion would be to lightly verticut or groom on a regular basis, roll (for the purpose of providing a smoother surface), lightly topdress frequently, and apply iron to minimize the color contrast. None of these practices will eliminate the problem, but hopefully help you get through this seedhead period.