Chemical and Biological Alternatives for Soil Disinfestation in Strawberry Production

After the phase-out of methyl bromide in the European Union, soil disinfestation has involved the use of mixtures of 1,3-dichloropropene (1,3-D) and chloropicrin (PIC), or the stand-alone use of chloropicrin, 1,3-D, methyl isothiocyanate-generating compounds, dimethyl disulfide (DMDS) and methyl iodide. However, in compliance with European regulations the future use of these products is highly uncertain. A lack of suitable fields for strawberry production compels strawberry growers to develop novel soil disinfestation techniques that will maintain farm profitability well in to the future. In order to meet both economical and socio-ecological aspects of prospective soil management measures, field plots were treated with chemical or biological agents. For three years, field trials were conducted using a plasticulture system with the cultivar 'Elsanta'. Chemicals used were 1,3-D, PIC, methyl isothiocyanate generating agents, DMDS and methyl iodide. Both simple as combined applications, different dosages and full field or shank application were investigated. Biological alternatives consisted of biofumigation (leek-broccoli-cauliflower), Caliente (liquid organic fertilizer with mustardseed adjuvant) and Herbie 22 (fermented material creating anaerobic soil conditions). In addition, some soil improvers (Myc 4000 - Biovin - Colonize AG) were used in combination with these biological agents. Whereas all chemical agents resulted in greater strawberry production, the biological agents only gave similar or less production in comparison with the untreated control. Nevertheless, all treatments resulted in a reduction of harmful nematode populations. Effects on Verticillium occurrence were ambiguous. Reducing the amount of active ingredients by shank application can only be advised in low risk situations. Although not as effective as chemical soil disinfestation, biologic alternatives may have a promising future in strawberry production.