Pseudomonas fluorescens strains selectively suppress annual bluegrass (Poa annua L.)

• Naturally occurring soil bacteria selectively inhibit annual bluegrass (Poa annua L.).
• Pseudomonas fluorescens strains produce compounds that suppress annual bluegrass.
• The bacteria reduces weed root elongation, tiller formation, and competitive ability.

Annual bluegrass (Poa annua L., ABG) is a cool-season annual grass that is a major weed species in turf, turfgrass-seed and sod production, and golf courses of the western United States. The life cycles of ABG and TG are very similar, but ABG is typically more competitive. Because these plants are so similar, selective control using conventional methods is limited. Pseudomonas fluorescens biovar B strain XJ3, biovar B strain XS18, and biovar A strain LRS12 are naturally-occurring soil bacteria that suppress ABG growth. These bacterial strains do not inhibit the growth of desirable turf species, other crops, or native plants. When applied to the soil and/or seeds in the fall, the bacteria establish in the soil community and increase in numbers during the cool temperatures of fall and spring, coinciding with the early root growth of ABG. These bacteria grow along roots and deliver a compound that inhibits root formation, root growth, and tiller initiation of ABG. The bacteria can also be used in combination with herbicides to inhibit the growth and seed production of standing ABG. Bacteria that selectively suppress ABG can be used to reduce the weed-seed bank in golf courses, lawns, turf, and turf-seed production. These bacteria add a formidable tool in the toolbox to fight invasive grass weeds, while limiting the need for tillage and herbicides for weed control.