Review paper on the composting of organic waste to eliminate plant pathogens and nematodes
Composted organic wastes are increasingly used by the horticultural and agricultural sectors and concerns have been raised about the possible presence of plant pathogens and nematodes in these composts. A review paper has recently been published by Noble & Roberts (2004), on the basis of information published in the literature, about the effects of temperature/time combinations and other sanitizing factors during composting on 54 plant pathogens and nematodes. Among pathogens and nematodes reviewed, the following are regulated pests in the EPPO region: Synchytrium endobioticum, Verticillium albo-atrum, V. dahliae, Phytophthora cinnamomi, P. ramorum, Clavibacter michiganensis subsp. michiganensis, Ervinia amylovora, E. chrysanthemi, Ralstonia solanacearum, Tomato spotted wilt tospovirus, Globodera pallida, G. rostochiensis, Meloidogyne chitwoodi. It is noted that in most papers reviewed, pathogen survival was determined by bioassays of unknown sensitivity and minimum detection limits of 5 % or more. In most cases reviewed, it was found that a peak temperature of 64-70°C during 21 days was sufficient to reduce numbers of pathogens and nematodes below the detection limits of the tests used. Some organisms appeared as more temperature-tolerant (e.g. Plasmodiophora brassicae, Fusarium oxysporum f. sp lycopersici Macrophomina phaseolina and a few viruses). In particular, Synchytrium endobioticum survived in water at 60°C for 2 h, but was not examined in compost. In many studies reviewed, the potential survival of plant pathogens in cooler zones of composts (particularly when compost is not turned) has not been quantified, although this may be an important risk factor. The authors concluded that for the moment, there is still insufficient data to produce comprehensive temperature-time matrices for the elimination of specific plant pathogens by composting.
Noble R, Roberts SJ (2004) Eradication of plant pathogens and nematodes during composting: a review.
Plant Pathology, 53(5), 548-568.