Biological Control of Annual Bluegrass (Poa annuaL.) with a Japanese Isolate ofXanthomonas campestrispv.poae(JT-P482)

Abstract

To select a biological control agent for annual bluegrass (Poa annua), 14 isolates ofXanthomonas campestrispv.poae,isolated from annual bluegrass in prefectures throughout Japan, were compared for pathogenicity and then examined for their safety toward desirable turf grasses such as creeping bentgrass (Agrostis palustris) and Kentucky bluegrass (Poa pratensis). One isolate, JT-P482, was found to be the most effective pathogen of annual bluegrass. It did not produce any symptoms in desirable turf grasses. By applying JT-P482 suspension to precut annual bluegrass, we obtained >75% weight loss (due to plant wilting and death) compared to uninoculated controls. The optimal cell concentration used in these experiments was >108CFU/ml in an application volume of 100–400 ml/m2. Rates of infection were accelerated by applying larger volumes of inoculum. At 25°C/20°C (day/night) annual bluegrass wilted severely in 7–10 days, but lower temperatures caused a loss of efficacy, showing that temperature is an important factor for effective control. Inoculation tests in zoysia (Zoysia tenuifolia) greens, in the fall, with a rate of 109CFU/ml at 400 ml/m2, resulted in over 90% disease severity the following spring. These experiments indicated thatX. campestrispv.poaehas great potential for controlling annual bluegrass without harming desirable turf grasses.