Anaerobic disinfestation of tare soils contaminated with Ralstonia solanacearum biovar 2 and Globodera pallida

Abstract

Tare soil is soil attached to harvested products like potato tubers. Tare soil becomes a considerable waste stream after storage, washing and processing of harvested products. There is a high risk on contamination of tare soils with (quarantine) phytopathogens, because of import of harvested products from different regions of the world. Disinfestation is necessary to make tare soils applicable for agricultural production. Anaerobic (non-chemical) soil disinfestation (ASD) and inundation are suitable methods to disinfest tare soils. Two different soils (marine loam and glacial sand) were either treated with five (2011) or four (2012) treatments and these were: (i) no treatment (control), (ii) freshly cut grass, (iii) Herbie 7025, (iv) inundation (five cm water on top of the soil surface), and (v) combination of Herbie 7025 and inundation (2011 only). Containers with treated and untreated soils were inoculated with two quarantine phytopathogens, Ralstonia solanacearum biovar 2 and Globodera pallida. After soil inoculation, the containers were airtight closed and only opened for destructive sampling after 84 days. Then, soils were analysed for the presence of R. solanacearum biovar 2, using immunofluorescence colony staining, and for the presence of viable G. pallida eggs, determined by the number of juveniles hatched from eggs and lured to potato root exudate. Strong (> 99.4 %) declines of both pathogens in treated versus the appropriate control soils were observed. Repetition of the experiment revealed the same pattern and therefore it was concluded that ASD and inundation, as separate treatments, have promise for remediation of tare soils from contaminating quarantine pathogens.