Research
IPM Strategies for Horseradish Diseases Horseradish is grown for its white flesh and pungent roots. Over the past 25 years, the horseradish growers have experienced internal discoloration in horseradish roots, causing up to 100% yield losses. Root discoloration of horseradish is a complex disease problem caused by soil-borne V. dahliae, V. longisporum, and Fusarium solani. At present, there is no method available to provide an effective control of this disease. Studies during the past six years showed that a primary inoculum source for root infection is infected, but asymptomatic to naked eyes, is horseradish sets (lateral roots), which are saved by growers to plant in the following season. The studies also revealed that symptoms of internal discoloration of horseradish roots caused by soil-borne inoculum of the pathogens become visible after about three months from the time of contact of the pathogen with the root. Fungicide fludioxonil (Maxim 4FS or Maxim Potato WP) and biofungicide Trichoderma virens (G-41/ABM 127 or SoilGard 12 G), applied to the pathogen-free sets, protect horseradish roots against the soil-borne inoculum of the pathogens for approximately 12 weeks. Pathogen-free horseradish sets can now be generated easily by tissue culturing at the University of Illinois. Since horseradish sets are usually planted in May and harvested during September-November. Application of either fungicide fludioxonil or biofungicide Trichoderma virens to tissue culture-generated sets, protect roots in the field through July. Remaining period of the growing season conducive for development of the disease (August-September) is not long enough for infection of the roots and expression of the discoloration. For more information on controlling internal discoloration of horseradish root, refer to the PUBLICAITON.