SOIL BACTERIA AS SELECTIVE BIOLOGICAL-CONTROL AGENTS OF WINTER ANNUALGRASS WEEDS IN WINTER-WHEAT

Many winter annual grass weeds, such as downy brome (Bromus tectorum L .) and jointed goatgrass Aegilops cylindrica Hose.), are difficult to control selectively in winter wheal (Triticum aestivum L.) grown in th e central and western US. The difficulty is due partially to a lack of selective chemical herbicides. Bacteria were isolated from soil and p lant roots and evaluated for inhibition of germination and root and sh oot growth of both weeds and wheal. Laboratory bioassays identified 16 2, 202, and 129 isolates that inhibited root growth of downy brome, Ja panese brome (B. japonicus Thunb. ex. Murr.), and jointed goatgrass, r espectively, Nine isolates inhibited downy brome shoot and root growth in soil in pot studies. In a field study established in the fall of 1 990 under adverse environmental conditions (high temperature/low moist ure), application of two isolates increased winter wheat yields as com pared to untreated wheat (P = 0.10).