Effect of Xanthomonas campestris pv. poae (JT-P482) on the Growth and Seed Production of Annual Bluegrass (Poa annua L.).

Abstract

To ascertain the most effective use of Xanthomonas campestris pv. poae (JT-P482) treatment for the control of annual bluegrass (Poa annua L.), pot-experiments in the greenhouse and in the field were conducted from 1993 to 1994. JT-P482 appeared to have merit as a management tool for the reduction of annual bluegrass growth, tiller numbers and seed production. Greenhouse experiments indicated that a 20°C/15°C day/night temperature regime enabled JT-P482 to effectively produce heavy wilting or plant death at cell concentrations higher than 108cfu/ml. This effectiveness continued for 3 months after the initial treatment. In the field pot experiments, applications of JT-P482 in early winter alone (December 1) and in spring alone (April 10), at cell concentrations of 108 and 109cfu/ml were very effective in suppressing seed production (77-85% and 84-88%, respectively). Moreover treatments administered in early winter and again in spring were found to significantly suppress (over about 85%) annual bluegrass seed production even at 107cfu/ml concentrations. However, of all concentrations (106 to 109cfu/ml), 108 and 109cfu/ml were most effective in suppressing seed production (about 94%). If seed suppression of 85% or more is considered to be acceptable for practical purposes, 109cfu/ml concentration in the early winter treatment, 108 and 109cfu/ml concentrations in the spring treatment, and concentrations higher than 107cfu/ml in repeated treatments can be highly effective.