Approaches and techniques for control of exotic annual grasses are a high priority in rangelands including sagebrush steppe. Strains of the soil bacterium Pseudomonas fluorescens have been proposed to be selectively pathogenic to multiple species of exotic annual grasses (“Pf,” weed-suppressive bacteria, “WSB”). However, defensible tests of the target and nontarget effects of these WSB strains in the field are needed. We evaluated the effects of D7 and MB906 strains of Pf WSB in sagebrush steppe invaded by cheatgrass (Bromus tectorum L), medusahead (Taeniatherum caput-medusae L. Nevski), and other exotic annual grasses. We evaluated the WSB strains with and without herbicides (imazapic, rimsulfuron) or discing to mix surface-spray of the WSB into deeper soils, and we replicated these tests in three ecoregions that differed in soils and climate. Over 3 yr after treatment, neither WSB strain affected cover of exotic annual grasses, perennial bunchgrasses, or the total community, either with WSB alone or in combination with herbicides or discing. WSB has received considerable attention and is being applied across large rangeland areas, but the WSB strains and methods applied here were ineffective. We recommend any future use of WSB be applied in an experimental fashion, with experimental design and measurement of responses, until its effects can be proven.

在包括鼠尾草草原在内的牧场中，控制外来一年生禾草的方法和技术是高度优先的工作。已提出土壤细菌荧光假单胞菌菌株对多种外来一年生禾草（“ Pf”，杂草抑制细菌“ WSB”）具有选择性致病性。但是，需要在现场对这些WSB菌株的靶标作用和非靶标作用进行可靠的测试。我们评估了D7和MB906菌株Pf WSB在鼠李草（Bromus tectorum L），medusahead（Taeniatherum caput-medusae）侵染的鼠尾草草原中的作用L. Nevski）和其他奇异的一年生禾草。我们评估了有无除草剂（吡虫啉，利福磺隆）或有无将WSB的表面喷雾混合到更深土壤中的WSB菌株，并在土壤和气候不同的三个生态区域中重复了这些试验。在处理3年后，无论是单独使用WSB还是与除草剂或盘根一起使用，WSB菌株均不会影响外来一年生草，多年生束草或整个群落的覆盖率。WSB已经受到相当大的关注，并且正在大范围的草地上应用，但是此处使用的WSB菌株和方法无效。我们建议将来将WSB的任何使用以实验方式进行，并进行实验设计和响应测量，直到可以证明其效果为止。