Vol. 54—2000 - NorthEastern Weed Science Society

Xanthomonas campestris pv. poannua EFFICACY ON THE ANNUAL
BIOTYPE OF Poa annua.
J. C. Cook, J. C. Neal, and F. H. Yelverton'
ABSTRACT
Field evaluations were conducted to determine the efficacy of the bacterial
pathogen, Xanthomonas campestris pv. poannua (Xcp), on the annual biotype of
annual bluegrass (Poa annua ssp. annual. Xcp innoculum (strain MB245l was
produced by EcoSoil Inc. Target inoculation concentrations of 10 7 and 10· cfu's
per ml were applied weekly or biweekly for six weeks. Applications were made at
200 gallons per acre w~h an air-pressurized sprayer. Visual evaluations for
annual bluegrass control were recorded weekly. Add~ionally, percent seedhead
suppression was recorded at the time of peak seedhead production, and percent
cover of annual bluegrass was recorded on the last rating date of May 25, 1999.
There were no significant differences between weekly and biweekly inoculations.
Inoculation concentrations of 10 7 cfu's per ml did not control annual bluegrass.
Four weeks after in~ial inoculation, plots with 10· cfu's per ml began to exhib~
disease symptoms. Weed control increased over time to 68% by May 25, 1999.
Inoculation concentrations of 10· cfu's per ml provided 88% seed head
suppression on May 17, 1999. Percent cover of annual bluegrass on May 25,
1999 was reduced by 51.6% as compared to the untreated. No further data were
collected because ofthe decline of the untreated annual bluegrass due to high
temperatures and drought.
, Department of Horticuttural Science and the Department of Crop Science, North
Carolina State Univers~
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