Consistency of control of damping-off of cucumber is improved by combining ethanol extract of Serratia marcescens with other biologically based technologies

Disease control tactics that rely less on synthetic pesticides are needed that are consistently effective in soils that vary with regard to their biotic and abiotic components. An ethanol extract of Serratia marcescens N4-5, when applied as a cucumber seed treatment, effectively suppressed damping-off of cucumber caused by Pythium ultimum in a natural sandy loam soil and a natural sand soil but not in a natural loam soil. A combination treatment containing seed treatment with this N4-5 ethanol extract and a drench containing Trichoderma virens GL21 improved disease control performance relative to individual application of both of the treatment components. Plant stand associated with this combination treatment was significantly greater than the no-treatment control in all three natural soils at all levels of pathogen inoculum used. In some cases plant stand associated with this combination treatment was significantly greater than that resulting from individual application of N4-5 ethanol extract or T. virens GL21. Data presented here indicate that strategic combinations of biologically based disease control tactics can increase consistency of performance in multiple soils that vary in biotic and abiotic characteristics.