CAPACITY OF COMPOSTS MADE FROM AGRICULTURE INDUSTRY RESIDUES TO SUPPRESS DIFFERENT PLANT DISEASES

Composted residues from different agricultural industries that are used as plant growth media have been shown to suppress different plant diseases. Those media are: cork compost (used alone or mixed with rice hulls); grape marc compost; olive marc and cotton gin trash (2/3, v/v) composted and mixed with rice hulls (1/1, v/v); and spent mushroom composted and mixed with peat or with rice hulls (1/1, v/v). This disease suppressive capacity was evaluated in bioassays involving pathogen inoculation and subsequent development in growth chambers or greenhouses. The diseases suppressed were tomato (races 1 and 2) and carnation (race 2) Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici and Fusarium oxysporum f. sp. dianthi respectively, and three cucumber diseases caused by Pythium aphanidermatum, Rhizoctonia solani and Botrytis cinerea. In order to compare severities or incidences in other plant growth media, development of diseases in light peat, vermiculite and/or coir fiber was also evaluated. Fusarium wilt severity was reduced by 99.9% in tomato and 99.2% in carnation. The most effective compost in controlling these diseases was grape marc compost. All the composts suppressed Pythium damping-off even with different maturation times. Mature grape marc compost showed the greatest reduction in severity of this disease (97.8%). Rhizoctonia damping-off bioassays showed that suppressive capacity increases over time after composting, being mature cork compost the most suppressive (97.2% reduction). Finally, the severity of Botrytis cinerea was also reduced by these composts, showing their capacity to suppress both soil-borne and airborne diseases.