Evaluation of compost teas from matured agricultural waste, vermicompost and solid municipal waste composts to suppress bacterial wilt of potato

Bacterial wilt caused by Ralstonia solanacearum is an economically important soil borne disease that limits potato production worldwide. We tested the effectiveness of compost tea to suppress this disease on potato plants grown in soils artificially inoculated with a virulent isolate of R. solanacearum in a greenhouse experiment in Ethiopia. Soil drenches of nonaerated teas prepared from three types of matured compost sources (agricultural waste, vermicompost and solid municipal waste) were evaluated at three application times (seven days before inoculation, at time of inoculation and seven days after inoculation) in a randomized complete block design. The compost tea treatments attained variable levels of disease suppression. Based on the disease severity index, the agricultural waste compost tea applied at the time of inoculation resulted in the highest disease suppression at the conclusion of the experiment and also resulted in the least disease throughout the experiment (based on the area under the disease curve). Vermicompost tea had the least suppressive effect on symptom development and its application at time of inoculation resulted in the highest disease severity index ·of all treatments. Despite a higher final disease severity index, area under the disease curve values for the solid municipal waste compost tea at all application times were lower than the controls and most of the other treatments. This study suggests that some non-aerated compost teas may provide cheap and effective biological control, however the type of compost and timing of application has a substantial influence on effectiveness.