Integrated Management of Crop Health in Response to Climate Variation in Commercial Open Field Tomato Production: Lessons Learned from the South African Experience (2003-2010)

South African open field tomato production occurs primarily in the Limpopo province and contributes significantly to the socio-economic stability of thousands of employees, suppliers and their dependents. Since 2003, these South African tomato producers practiced intensive open field tomato production using a combination of synthetic and organic crop management technologies. The objective of this study was to analyze these production practices and its effect on yield and marketability in terms of prevailing climate conditions. We studied these interactions for three different planting times within the year over an eight-year period by means of multivariate statistical techniques, including Classification and Regression Tree (CART) analysis. The results showed that complex interactions between biotic and abiotic variables influenced tomato yield and quality in each planting window. No crop or soil management option could defer the negative impact of climate variation on yield within unsuitable planting windows. The complex interaction between ecology and economics was confirmed. The ecosystem impact quotient (EIQ) of pesticide usage was significantly higher (P<0.001) in the unsuitable planting window due to disease-conducive climate conditions and the producer's response to subsequent problems. However, market prices were usually higher for produce planted in the unsuitable planting window. Increasing production costs has since forced these producers to abandon the unsuitable planting time and explore geographical alternatives in order to maintain profitable year-round tomato supply. In response to disease-conducive climate conditions, the sustained but sensible use of synthetic pesticides ensured high yield in the suitable planting windows. Although on-farm produced organic crop protectants were applied, efficacy was inconsistent. Planting time optimization was the best systems-level intervention for mitigating the risks of climate variation. At the practical level, sustainable open field tomato production depended on the integration of synthetic crop nutrition, synthetic and organic crop protection, disease-resistant cultivars, and cultivation in healthy soils.