Bacterial wilt is an increasing disease of annual bluegrass (Poa annua) throughout New England. The disease is caused by the only known bacterial disease of turfgrasses in the United States. First identified as a disease of vegetative creeping bentgrass, bacterial wilt now appears to be restricted to annual bluegrass putting greens. The disease may also appear, however, on collars and/or approaches. Bacterial wilt may appear during the spring, but often will persist throughout the summer. The disease is favored by periods of heavy rainfall or overcast and cloudy weather. The disease may subside during sunny and dry weather, but can rapidly resurge following rain. In situations where the disease is chronically severe, renovation of annual bluegrass putting greens with creeping bentgrass may be necessary.
Bacterial wilt tends to be more severe on shaded and/or poorly drained greens.
Due to their inability to directly penetrate cells, bacteria must enter the plant through natural opening such as stomata or through wounds. Once inside the plant, the bacteria inundate the cells and restrict the natural flow of water and nutrients through the vascular tissues. Initial symptoms appear as wilt and individual infected annual bluegrass plants quickly turn reddish-brown or yellow, and die (Fig 1). Collapsed plants generally appear as whitish-tan, dime-sized spots. During a severe infection, large areas can be killed in a non-uniform pattern within a few days.