Field performance of a weed-suppressing Serratia plymuthica strain applied with conventional spraying equipment

In previous glasshouse experiments, the soil bacterium Serratia plymuthica, strain A153, showed strong growth-suppressing activities against a range of broad-leaved weeds after foliar spraying. In field tests of this strain in spring wheat, spring barley and potatoes, variable effects were achieved on a range of weeds including Chenopodium album, Stellaria media, Polygonum convolvulus and Galeopsis speciosa. At one site, good suppression of C. album was observed when the strain was applied in a tank mix with another bacterial isolate or with reduced doses of a herbicide. Effects on weeds appeared to be independent of the application volume (1000, 600, 500 l ha(-1)), but weeds were in some cases more strongly suppressed at higher bacterial doses. Barley yields were somewhat reduced by the bacterial application, but wheat yields were less affected. Although S. plymuthica suppressed certain weeds when applied in the field in a simple aqueous formulation and with conventional spraying equipment, the level of weed suppression was unsatisfactory from a practical standpoint.