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

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

Summary

Horseradish (Armoracia rusticana) is a root crop cultivated for its pungent, white fleshy roots. Approximately half of the total horseradish crops produced in the United States is grown in Illinois. Internal discoloration of horseradish roots, caused by Verticillium and Fusarium species, is a disease complex and is a serious threat to horseradish production as causing up to 100% yield losses. Use of fungicides and/or soil fumigation has been ineffective for control of this complex disease. Crop rotation alone is of limited value due wide host range of the pathogens and the pathogena’s resilient surviving bodies in soil indefinitely. Also, the pathogens are set-borne, which makes the ecology of the diseased more complicated and difficult to control. There are no commercial horseradish cultivars resistant or tolerant to the internal root discoloration available. Our preliminary studies showed that the set-born inoculum of the diseases can be eradicated by hot-water treatment (thermo-therapy). Also, plants grown from pathogen-free sets can be protected against soil-borne inoculum of the pathogens by application of a biofungicide, either G-41/ABM 127 (Trichoderma virens-G41/ABM 127 isolate) or SoilGard 12G (Trichoderma virens-12 G isolate), onto sets prior to planting.

This is a two-year project to develop an effective strategy for management of the most internal discoloration of horseradish roots.

The specific objectives of this research project are:
(i) to evaluate and demonstrate the effectiveness of thermo-therapy for control of set-borne inoculum of the internal root discoloration;
(ii) to demonstrate the effectiveness of the biofungicides for control of the internal root discoloration;
(iii) to demonstrate effectiveness of an IPM approach to solve the complex internal discoloration disease of horseradish root; and (iv) to establish a sustainable horseradish production system.

The results of this research will be presented to growers, food processors, extension personnel, and at the regional and national meetings. Results also will be published in newsletters, websites, and refereed journals. Implementation of the results of this research is expected to be rapid and the growers will benefit from findings in this research.

Objectives/Performance Targets

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

The short term outcomes of this research would be developing an effective thermo-therapy method for eradication of set-borne inoculum for the internal discoloration of horseradish roots without affecting set germination and plant vigor, demonstrating importance of set-borne inoculum in initiating the internal discoloration of horseradish roots, determining/demonstrating effectiveness of biofungicides for protecting plants in the field against soil-borne inoculum of the internal discoloration of roots, and effectiveness of an integrated approach for management of the internal discoloration of horseradish roots. The intermediate and long term outcome of this project would be to demonstrating the effectiveness of IPM strategies for solving plant disease problems, such as the complex internal discoloration of horseradish roots, and to help establish a sustainable horseradish production system.

The research is expected to help to establish a sustainable horseradish production in Illinois, as well as in the US. The strategy developed in this research will be rapidly implemented because:
(i) there is no effective method for control of internal discoloration of horseradish roots is available,
(ii) the proposed strategy can easily be implemented by the growers,
(iii) the method is very cost/effective (about 2% of farm-gate value of the cop),
(iv) the management approach is environmentally safe and can be used in organic horseradish production, and
(v) all materials used in implementing the strategy are commercially available.

Accomplishments/Milestones

In 2007, set treatment at 48°C for 20 or 30 min significantly reduced percentage of germination in cultivars 15K and BTW compared to untreated sets and the sets treated at 46°C and 47°C. Similarly, set treatment at 48°C for 20 or 30 min significantly reduced percentage of germination in cultivars 15K and BTW compared to untreated sets and the sets treated at 46°C, 47°C, and 48°C for 10 min. For cultivar 1573, however, only set treatment at 48°C for 30 min reduced percentage of germination significantly when compared to all the other treatments and control. For cultivar 1722, set treatment at 48°C for 30 min affected germination significantly compared to other treatments but not untreated control.

Incidence of the internal root discoloration. The results of the field studies on using fungicides and biocontrol agents showed that hot-water treatment of sets reduced the incidence and severity of internal discoloration of horseradish roots.

Both fungicides (Maxim 4FS and Maxim Potato) and biocontrol agents SoilGard and G-41 protected plants against the pathogens causing internal discoloration of roots in fields without any adverse effects on set germination or plant vigor. Serenade MAX reduced germination of sets when applied onto hot-water treated sets. Disease incidence (percentage of roots affected) and disease severity (percentage of root surface area discolored at the cross section) were 68.75 and 7.51%, respectively, in plants grown from non-heat treated and non-fungicide/biocontrol-agent treated sets compared to 13.75 and 0.87% of the plants grown from hot-water treated and G-41 treated sets, and 20.0 and 1.06% of the plants grown from hot-water treated and Maxim Potato treated sets in Wisconsin trials. In Illinois, disease incidence and severity of plants grown from non-heat treated and non-fungicide/biocontrol-agent treated sets were 57.5 and 3.17%, respectively, compared to 4.17 and 0.21% of plants grown from sets treated with hot-water treated and G-41, and 7.50 and 0.46% of the plants grown from sets grown with hot-water and Maxim Potato.

Impacts and Contributions/Outcomes

The research is expected to help to establish a sustainable horseradish production in Illinois, as well as in the US. The strategy developed in this research will be rapidly implemented because:
(i) there is no effective method for control of internal discoloration of horseradish roots is available,
(ii) the proposed strategy can easily be implemented by the growers,
(iii) the method is very cost/effective (about 2% of farm-gate value of the cop),
(iv) the management approach is environmentally safe and can be used in organic horseradish production, and
(v) all materials used in implementing the strategy are commercially available.

Collaborators: