Effects of solarization of soil on nematode and fungal pathogens at two sites in victoria

The effect of covering soil with transparent polyethylene sheets, known as soil solarization, on the viability of plant pathogens was determined. The treatment was tested in mid-summer on sandy loams in N.W. and S. Victoria. Columns of moist soil were inoculated with one of a variety of pathogens, viz. Fusarium oxysporum, Pythium irregulare, Plasmodiophora brassicae, Sclerotium cepivorum, S. rolfsii, Sclerotinia minor, Verticillium dahliae and the nematodes Macroposthania xenoplax, Meloidogyne javanica, Pratylenchus penetrans and Tylenchulus semipenetrans. Columns were placed vertically in soil, and then treated either for 4 weeks in N.W. Victoria, or 6 weeks in S. Victoria.Preliminary laboratory tests showed that pathogens were killed by temperatures within the range 38–55°C. The relative sensitivities of pathogens to fluctuating soil temperatures were similar at both sites. The most sensitive were the nematodes, and the fungi V. dahliae, S. cepivorum and S. minor, while F. oxysporum, P. irregulare and P. brassicae were the least sensitive. In N.W. Victoria treatment effects were apparent to 26 cm and most pathogens were not recovered from 0 to 11 cm. In S. Victoria treatment effects were apparent to a depth of 16cm and most pathogens were not recovered from 0 to 6cm.