Survival of human and plant pathogens during anaerobic mesophilic digestion of vegetable, fruit, and garden waste

Five pathogens were added to vegetable, fruit and garden waste and their survival was studied during mesophilic (maximum temperature 40 °C) anaerobic digestion. Digestion during 6 weeks took place with a 50/50% (v/v) ratio of digested and fresh, undigested material, respectively. Survival of the plant pathogens Fusarium oxysporum f.sp. asparagi and Ralstonia solanacearum, and of the human pathogen Salmonella typhimurium was below the detection levels, and survival of the plant pathogen Plasmodiophora brassicae was low in one experiment and below the detection level in two replicates. In addition, numbers of Enterobacteriaceae originally present in the waste decreased significantly during digestion. However, sclerotia of the plant pathogen Sclerotium cepivorum recovered from the digestion vessel were, at least in part, viable. It is concluded that many pathogens may be inactivated readily, but that anaerobically digested compost may involve some significant phytohygienic problems. From this study, it can be concluded that vegetable, fruit and garden waste containing onions infected with S. cepivorum should be avoided.