Solar-heating soil for control of damping-off diseases

Abstract Solar-heating (45–52°C) moist soil under 50μm thick clear plastic sheeting during summer (Jan.–Feb.) significantly reduced pre-emergence damping-off disease of Pinus radiata D. Don (radiata pine) and Eucalyptus obliqua L'Herit (messmate and stringybark) seed, and also post-emergence mortality among P. radiata seedlings. Phytophthora cinnamomi Rands, Fusarium oxysporum Snyder and Hansen, and Pythium sp. could not be re-isolated from artificially inoculated pine roots after exposure to the solar-heating treatment. Natural infectious propagules of P. cinnamomi were also undetectable in solar-heated soil for up to 16 months following treatment, though infectious propagules of Pythium were detected at low level. The treatment also controlled 11 weed species. Solar-heating a potting mixture temporarily suppressed disease incidence in nursery stock, possibly due to an increase in antagonistic microorganisms. Solar-heating moist soil appears to be particularly attractive in forest nursery practice, as it provides a simple, effective, non-toxic and non-polluting technique for control of soil-borne diseases and weed species.