Developing an Effective Strategy for Management of Internal Discoloration of Horseradish Root

This study was conducted to develop an effective method for management of internal discoloration of horseradish roots. Internal discoloration of horseradish is a disease complex caused by at least three fungi, Verticillium dahliae, V. longisporum, and Fusarium solani. These fungi are carried in the propagating roots (set-borne inoculum) and also survive in the soil (soil-borne inoculum). 

The first step for management of the disease was to develop a reliable method to eradicate set-borne inoculum of the pathogen. This was achieved by treating the sets in hot water. The most effective treatment for eradication of set-borne inoculum, without adversely effecting set germination or plant vigor, was determined to be hot-water treatment of horseradish sets at 47ºC for 20-30 min. 

The second step for management of the disease was protecting plants against soil-borne inoculum in the fields. This goal was fulfilled by set treatment with the fungicide fludioxonil (Maxim 4FS or Maxim Potato WP) or biocontrol agent Trichoderma virens (SoilGard 12G or G-41) prior to planting sets. By combining the hot-water treatment of thesets and application of the fungicide or biocontrol agent onto the sets the internal discoloration of horseradish roots was effectively managed.

Objectives/Performance Targets

This was a two-year project to develop an effective strategy for management of the internal discoloration of horseradish roots. The specific objectives of this research project were:to evaluate and demonstrate the effectiveness of thermo-therapy for control of set-borne inoculum of the internal root discoloration;to demonstrate the effectiveness of the biofungicides for control of the internal root discoloration;to demonstrate effectiveness of an IPM approach to solve the complex internal discoloration disease of horseradish root; andto establish a sustainable horseradish production system.

Impact of Results/OutcomesThe research is expected to help to have a sustainable horseradish production in Illinois, as well as other horseradish growing areas in the US because:there is no effective method for control of internal discoloration of horseradish roots is available, the proposed strategy can easily be implemented by the growers;the method is very cost/effective (about 2% of farm-gate value of the crop);the management approach is environmentally safe and can be used in organic horseradish production too; andall materials used in implementing the strategy are commercially available.

Economic Analysis

Horseradish is a high-value crop. Farmgate value of horseradish ranges from $3,000 to more than $6,000 per acre (~ $7,400 - $15,000 per ha). Gross value of horseradish products ranges from $6,000 to more than $10,000 (~ $15,000 - $25,000 per ha). Horseradish has nutritional and medical values. The findings of this study are expected to have a positive impact on grower’s income, economy of the horseradish grower’s communities, and agricultural economy of Illinois and other states. The costs of implementing this strategy is approximately $50 per acre.

Want more information? See the related SARE grant(s) GNC07-074, Developing an Effective Strategy for Management of Internal Discoloration of Horseradish Root.