BIOLOGICAL-CONTROL OF ANNUAL BLUEGRASS (POA ANNUA L) WITH A JAPANESE ISOLATE OF XANTHOMONAS-CAMPESTRIS PV POAE (JT-P482)

To select a biological control agent for annual bluegrass (Pea annual, 14 isolates of Xanthomonas campestris pv. poae, isolated from annual bluegrass in prefectures throughout Japan, were compared for pathogeni city and then examined for their safety toward desirable turf grasses such as creeping bentgrass (Agrostis palustris) and Kentucky bluegrass (Pea pratensis). One isolate, JT-P482, was found to be the most effec tive pathogen of annual bluegrass. It did not produce any symptoms in desirable turf grasses. By applying JT-P482 suspension to precut annua l bluegrass, we obtained >75% weight loss (due to plant wilting and de ath) compared to uninoculated controls. The optimal cell concentration used in these experiments was >10(8) CFU/ml in an application volume of 100-400 ml/m(2). Rates of infection were accelerated by applying la rger volumes of inoculum. At 25 degrees C/20 degrees C (day/night) ann ual bluegrass wilted severely in 7-10 days, but lower temperatures cau sed 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 10(9) CFU/ml at 400 ml/m(2), res ulted in over 90% disease severity the following spring. These experim ents indicated that X. campestris pv. poae has great potential for con trolling annual bluegrass without harming desirable turf grasses. (C) 1997 Academic Press