|Mahaffee, Walter - Walt|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2004
Publication Date: 11/1/2004
Citation: Scheurell, S., Mahaffee, W.F. 2004. Compost tea as a container media drench for supressing seedling damping-off caused by pythium ultimum. Phytopathology. 94(11)1156-1163. Interpretive Summary: Compost tea is being increasingly used as an alternative plant disease control measure in commercial horticulture. It is produced by mixing compost with water and fermenting for a defined period, with or without added fermentation nutrients and either actively aerated (aerated compost tea, ACT) or not (non-aerated compost tea, NCT). Compost tea applied to foliage has been demonstrated to suppress a range of foliar diseases, however, the use of compost tea as a soil drench for seed or root rot suppression has received very little attention.
Technical Abstract: Aerated and non-aerated compost tea, produced with or without fermentation nutrients, was investigated for the suppression of P. ultimum damping-off of cucumber. Compost tea effectively suppressed damping-off in soilless container media. Both aerated compost tea (ACT) and non-aerated compost tea significantly reduced disease only when fermentation nutrients were added. The most consistent formulation for damping-off suppression was ACT fermented with kelp and humic acids. Producing ACT with a molasses-based fermentation nutrient solution inconsistently suppressed damping-off; evidence suggests that residual fermentation nutrients can interfere with disease suppression. Across all compost tea samples, there was not a significant relationship of bacterial populations, determined by active, total or cfu methods, to disease suppression. However, for all ACT produced without the molasses-based fermentation nutrient solution, there does appear to be a threshold of bacterial population level above which compost teas are suppressive.