Annual bluegrass is one of the five most widely distributed plants in the world. Annual bluegrass is more prolific and competitive under an ecological regime of close mowing, light frequent irrigation, high fertility, and moist soils. It is a winter annual that germinates in late summer/early fall, once soil temperatures have dropped below 70 degrees F. Seedlings mature in the fall, overwinter in the vegetative state, and produce seed in late spring and early summer. Some germination of annual bluegrass seed also occurs in the spring. The seed may lie dormant in the soil for many years before germinating, resulting in a significant build-up of indigenous seed overtime. It tends to be more prolific during wet seasons. Annual bluegrass often dies in the heat of the summer due to heat and drought stress, disease, and/or insect damage.
There are currently several products labeled for annual bluegrass control; however, there are limitations on the number of annual applications that can be made. Chemical control of annual bluegrass consists of either a rigorous preemergence program and/or a postemergence herbicide called ethofumesate (Prograss®). Prograss is most efficacious when applied in the fall using multiple applications. See label for specific recommendations. Velocity (bispyribac sodium) is a postemergence herbicide recommended for the selective removal of annual bluegrass in creeping bentgrass. This herbicide has been recently labeled by Valant Chemical Company. Of course, annual bluegrass patches can be spot treated with the non-selective herbicides glyophosate (Roundup) or glufosinate-ammonium (Finale) and then re-seeded.