Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2004
Publication Date: 6/6/2005
Citation: Zdor, R.E., Alexander, C.M., Kremer, R.J. 2005. Weed suppression by deleterious rhizobacteria is affected by soil type and formulation. Communications in Soil Science and Plant Analysis. 36:1289-1299.
Interpretive Summary: Certain environmental microorganisms and natural plant products are able to reduce the growth of weeds that interfere with crops and have the potential to reduce the amount of herbicides used for conventional weed control. We examined a known weed growth-inhibitory bacterium (deleterious rhizobacterium, DRB) and two natural products, corn gluten meal (CGM) and wheat flour, alone or combined with DRB for growth suppression of green foxtail and velvetleaf. Green foxtail and velvetleaf are very competitive weeds infesting corn, soybean, and grain sorghum and require annual herbicide applications for control. Wheat flour alone suppressed wheat growth in both soils but only green foxtail in sandy loam. The DRB alone or combined with wheat flour suppressed green foxtail growth in silt loam and sandy loam soils; however, velvetleaf was suppressed only in sandy loam when DRB was combined with wheat flour. DRB apparently increased weed suppression of wheat flour. Wheat seedling growth was promoted by DRB in silt loam but suppressed in sandy loam. CGM alone suppressed all seedlings except velvetleaf in silt loam. CGM was also toxic to the DRB; therefore, it cannot be considered a carrier for DRB in a weed biocontrol product. Results demonstrate that natural plant products and selected microorganisms have potential as integrated weed biocontrol methods. Also, results have important implications for scientists because several complex interactions involving formulation material, soil type, and cropping system must be considered in biocontrol development.
Technical Abstract: Rhizobacteria have been shown to suppress weed growth in field tests. This study compared the relative inhibitory action of the deleterious rhizobacterium (DRB) Pseudomonas fluorescens strain G2-11 formulated with the natural plant products, corn gluten meal (CGM) and semolina flour, towards wheat (Triticum aestivum), green foxtail (Setaria viridis), and velvetleaf (Abutilon theophrasti) seeds and seedlings in soil assays. Strain G2-11 was successfully established in semolina flour in inoculum preparation but was incompatible with CGM presumably due to antibacterial factors present. The effect of the DRB and plant products on seed germination and plant growth were influenced by soil, with the strongest effects seen in fine sandy loam. Semolina flour reduced root growth of wheat in both soils and green foxtail in fine sandy loam. Greatest seed germination reduction was by strain G2-11 on green foxtail. With the exception of wheat seedling growth, strain G2-11 improved the seed suppressive qualities of semolina flour. Results suggest that natural plant products alone and formulated with selected DRB may be important components for weed management considerations in sustainable agriculture.